Prof. Dr. rer. nat. Jürgen Vormann, born 1953, studied Science of Nutrition at the University Hohenheim, Stuttgart, Germany, where he also earned his Doctorate in Pharmacology and Toxicology of Nutrition. He achieved the „Habilitation“ for Biochemistry at the Institute of Molecular Biology and Biochemistry, University Clinics Benjamin Franklin, Free University Berlin, where he has the position of an extraordinary Professor. Main work areas are: biochemistry and pathophysiology of pharmacologically active food ingredients, acid-base-metabolism; more than 200 publications in scientific journals, monographs and textbooks. Prof. Vormann is head of the Institute for Prevention and Nutrition (IPEV) in Ismaning/Munich, Germany. The Institute is supervising clinical trials, develops teaching materials, and consults various pharmaceutical companies in the development of specific supplements within the area of nutritional medicine. Among others Prof. Vormann was president of the German Scociety for Magnesium-Research, Chairman of the Gordon Research Conference “Magnesium in Biochemical Processes and Medicine”, Ventura, USA, 2005, and is in the advisory board of various nutrition organizations.
Abstract: Evidence arguing for the existence of genes encoding for proteins directly involved in the transport of Mg2+ through the cytoplasmic membrane have accumulated over the last few years. Gene ACDP2 (ancient conserved domain protein 2; old name CNNM2, cyclin M2) is one such gene. ACDP2 is a distant homologue of the bacterial gene corC, which is known to be involved in cobalt resistance. We have previously demonstrated that the over-expression of the human Mg2+ carrier SLC41A1 partly complements the Mg2+-dependent growth deficiency of Salmonella strain MM281 (triple disruptant in genes: mgtA, mgtB and corA) cultivated in media containing growth non-permissive [Mg2+](e). We have used the same approach to examine whether over-expressed human ACDP2 has a similar efficacy to complement growth deficiency of the MM281 strain in media containing growth non-permissive [Mg2+](e). Two splicing variants of the ACDP2 gene have been tested. Here, we show that over-expressed isomorph 1 is efficient in restoring growth of the MM281 strain in media containing growth non-permissive [Mg2+](e), whereas isomorph 2 is not. Therefore, we conclude that ACDP2sp.v.1 is a functional Mg2+-transporting entity per se. Our conclusion is supported by the measurable Mg2+ influx seen in MM281 bacteria over-expressing ACDP2sp.v.1 but not in MM281 bacteria over-expressing ACDP2sp.v.2 or in cells transformed with the empty vector.
Abstract: Background. Previous experimental studies demonstrate that the acid-base balance influences mineral homeostasis by regulating the absorption of calcium and magnesium in the kidneys. No intervention studies are available on population samples. Aims. To study the urinary excretion of calcium and magnesium before and after an intervention with the aim of decreasing the acid load. Methods. Healthy subjects aged 50-75 years were recruited by advertising. Urinary calcium, magnesium and urea as well as blood pressure were measured before and after the intervention. This comprised taking tablets containing potassium hydrogen carbonate or potassium chloride (placebo) during 7-10 days. Results. There were significant relationships between the urinary excretion of urea and magnesium and calcium before the intervention. Comparing before and after intervention, the change in urinary excretion of urea was related to a change in urinary excretion of calcium and magnesium. There was a significant decrease in systolic as well as diastolic blood pressure both after administration of potassium hydrogen carbonate and citrate. Conclusion. The results confirm previous studies showing a relation between acid conditions in the body and the excretion of calcium and add new data on magnesium. A blood pressure decrease after potassium has been found in previous studies. This suggests an alternative for the treatment of moderately increased levels of blood pressure that should be further explored.
Abstract: The role of nutrition in human acid-base homeostasis has gained increasing attention in recent years. Although in healthy humans, homeostatic mechanisms and the kidneys' capacity to excrete acid equivalents can prevent strong diet-induced alterations in blood pH, even moderate increases in blood hydrogen ion levels as a result of unfavorable diet composition can have long-term consequences for the occurrence and progression of a number of diseases. The Second International Acid-Base Symposium, Nutrition-Health-Disease, provided deeper insight and updates in the scientific basis of the relation among diet, acid-base homeostasis, physiology, and pathophysiological consequences.
Abstract: OBJECTIVES: To evaluate whether renal net acid excretion capacity (NAEC) varies across different age groups and, specifically, whether it falls in elderly people. DESIGN: Cross-sectional observational study. SETTING: Community-based. PARTICIPANTS: Young participants were from the DOrtmund Nutritional and Anthropometric Longitudinally Designed Study, Dortmund, Germany; elderly participants were from Gothenburg, Sweden. MEASUREMENTS: Twenty-four-hour urine pH, net acid excretion (NAE), urinary phosphorus, total nitrogen excretion, and anthropometric data were measured in healthy elderly people (aged 55-75; n=85), young adults (aged 18-22; n=117), adolescents (aged 13-14; n=112), and prepubescent children (aged 6-7; n=217). NAEC was determined as 24-hour NAE adjusted for urine pH using the residual method. RESULTS: In elderly participants 24-hour urinary pH (5.9+/-0.53) was lower (P<.05) and NAE (60+/-27 mEq/d) higher (P<.05) than in the three other groups. In a regression model adjusted for age, sex, and body surface area, NAEC showed a clear decrease with age, with highest values in prepubescents and lowest in elderly participants. However, NAEC remained significantly lower only in elderly participants (P<.001) after the inclusion of total nitrogen excretion, a protein intake index, which was included because protein intake is known to modulate renal function. NAEC was approximately 8 mEq/d lower in healthy elderly participants than in young adults. CONCLUSION: The capacity to excrete net endogenous acid does not vary markedly from childhood to young adulthood but falls significantly with age, implying that elderly people may require higher daily alkalizing mineral intake to compensate for renal function losses.
Abstract: OBJECTIVE: In patients with nephrolithiasis, an inverse relationship between 24-h urinary pH (24h-UpH) and body weight has been reported. Whether body composition indices and 24h-UpH are similarly associated in healthy subjects needs investigation. DESIGN: Cross-sectional, retrospective analysis. SETTING: Dortmund, Germany and Gothenburg, Sweden. SUBJECTS: Healthy young adults (18-23 years; n=117) and elderly (55-75 years; n=85) having a mean body mass index (BMI) of 22.80+/-3.4 and 25.3+/-3.9 kg/m2, respectively. METHODS: Anthropometric data, 24h-UpH, and 24-h urinary excretion rates of net acid (NAE), creatinine, and urea were determined. After adjusting for urea (reflecting protein intake), renal creatinine output was used as a biochemical marker for muscularity. The BMI served as a marker of adiposity. RESULTS: NAE, body weight, and BMI were significantly (P<0.05) higher, and height and creatinine significantly lower in the elderly, whereas body-surface area (BSA) was not different. Step-wise multiple regression analysis using BSA-corrected urinary variables revealed NAE as the primary predictor of 24h-UpH (with R2 values of 0.64 and 0.68 in young adults and elderly, respectively, P<0.0001), followed by urea (P<0.0001), creatinine (P<0.05), and BMI (P<0.05 for the young adults and P=0.12 for the elderly). These associations were negative for NAE and BMI, and positive for urea and creatinine. CONCLUSIONS: Muscularity (i.e. creatinine adjusted for urea) and particularly in the group of young adults, adiposity (i.e. BMI) proved to be modest, but significant predictors of 24h-UpH. Future research should focus on more obese subjects in whom insulin resistance and particular kidney functions should also be examined to further substantiate the role of obesity in low-urine pH-associated conditions, for example, nephrolithiasis.
Abstract: To learn about the cellular processes involved in Mg(2+) homeostasis and the mechanisms allowing cells to cope with low Mg(2+) availability, we performed RNA expression-profiling experiments and followed changes in gene activity upon Mg(2+) depletion on a genome-wide scale. A striking portion of genes up-regulated under Mg(2+) depletion are also induced by high Ca(2+) and/or alkalinization. Among the genes significantly up-regulated by Mg(2+) starvation, Ca(2+) stress, and alkalinization are ENA1 (encoding a P-type ATPase sodium pump) and PHO89 (encoding a sodium/phosphate cotransporter). We show that up-regulation of these genes is dependent on the calcineurin/Crz1p (calcineurin-responsive zinc finger protein) signaling pathway. Similarly to Ca(2+) stress, Mg(2+) starvation induces translocation of the transcription factor Crz1p from the cytoplasm into the nucleus. The up-regulation of ENA1 and PHO89 upon Mg(2+) starvation depends on extracellular Ca(2+). Using fluorescence resonance energy transfer microscopy, we demonstrate that removal of Mg(2+) results in an immediate increase in free cytoplasmic Ca(2+). This effect is dependent on external Ca(2+). The results presented indicate that Mg(2+) depletion in yeast cells leads to enhanced cellular Ca(2+) concentrations, which activate the Crz1p/calcineurin pathway. We provide evidence that calcineurin/Crz1p signaling is crucial for yeast cells to cope with Mg(2+) depletion stress.
Abstract: Quinolone-induced chondrotoxicity in juvenile rats and multiple other species has been demonstrated previously. Identical damages can be induced in immature rats by feeding them a magnesium-deficient diet. The objective of the present study was to investigate whether, in reverse, oral supplementation with magnesium, vitamin E, or both can diminish the typical quinolone-induced arthropathy in juvenile Wistar rats. Four groups of 12 (6 male, 6 female) 24-day-old Wistar rats were each fed either normal feed (group A), a vitamin E-enriched diet (group B), a magnesium-enriched diet (group C), or a diet enriched with both vitamin E and magnesium (group D) for 10 days. All rats received two subcutaneous ciprofloxacin doses of 600 mg/kg of body weight on postnatal day 32. Two days later, the rats were sacrificed and cartilage samples from knee joints were examined under a light microscope for the presence of typical quinolone-induced joint cartilage lesions. In addition, magnesium, calcium, and vitamin E concentrations in cartilage and plasma were determined. In the samples from rats fed a normal diet (group A), 17 quinolone-induced joint cartilage lesions were observed. In groups fed an enriched diet, the incidence of specific lesions (n) was significantly lower: group B, n = 10 (41% reduction compared to the incidence for group A; P < 0.05); group C, n = 6 (65% reduction; P < 0.01); and group D, n = 3 (82% reduction; P < 0.01). In comparison to the standard diet, diets with magnesium and vitamin E supplementation resulted in significantly higher magnesium and vitamin E concentrations in plasma and articular cartilage. Supplementation with magnesium and vitamin E alone or in combination may relevantly diminish joint cartilage lesions induced by quinolones in immature rats, with an additive effect of combined supplementation. The data further support the proposed pathomechanism of quinolone-induced arthropathy and the crucial role of magnesium in immature joint cartilage.
Abstract: Magnesium and calcium deficiency in humans is related to a number of pathological phenomena such as arrhythmia, osteoporosis, migraine, and fatal myocardial infarction. Clinically established metabolic acidosis induces renal losses of calcium. In normal subjects, even moderate increases in net endogenous acid production (NEAP) impair renal calcium reabsorption but no information is available whether this also influences renal magnesium handling. The aim of the study was to examine the relation between NEAP and renal magnesium excretion in healthy, free-living, elderly subjects. The subjects (age 64 +/- 4.7 y, n = 85) were randomly selected from the population register in Gothenburg (Sweden). Magnesium, calcium, and potassium were measured in 24-h urine samples and NEAP was quantified as renal net acid excretion (NAE). NAE was positively correlated with excretions of magnesium (R(2) = 0.27, P < 0.0001) and calcium (R(2) = 0.30, P < 0.0001) but not potassium. When 24-h urinary magnesium excretion was adjusted for 24-h urinary potassium excretion, a biomarker for dietary potassium intake, the association between magnesium excretion and NAE remained significant (R(2) = 0.21, P < 0.0001). The significant association between potassium-adjusted magnesiuria and NAE suggests that the acid-base status affects renal magnesium losses, irrespectively of magnesium intake. Magnesium deficiency could thus, apart from an insufficient intake, partly be caused by the acid load in the body.
Abstract: Coenzyme Q10 is an essential cofactor in the electron transport chain and serves as an important antioxidant in both mitochondria and lipid membranes. CoQ10 is also an obligatory cofactor for the function of uncoupling proteins. Furthermore, dietary supplementation affecting CoQ10 levels has been shown in a number of organisms to cause multiple phenotypic effects. However, the molecular mechanisms to explain pleiotrophic effects of CoQ10 are not clear yet and it is likely that CoQ10 targets the expression of multiple genes. We therefore utilized gene expression profiling based on human oligonucleotide sequences to examine the expression in the human intestinal cell line CaCo-2 in relation to CoQ10 treatment. CoQ10 caused an increased expression of 694 genes at threshold-factor of 2.0 or more. Only one gene was down-regulated 1.5-2-fold. Real-time RT-PCR confirmed the differential expression for seven selected target genes. The identified genes encode proteins involved in cell signalling (n = 79), intermediary metabolism (n = 58), transport (n = 47), transcription control (n = 32), disease mutation (n = 24), phosphorylation (n = 19), embryonal development (n = 13) and binding (n = 9). In conclusion, these findings indicate a prominent role of CoQ10 as a potent gene regulator. The presently identified comprehensive list of genes regulated by CoQ10 may be used for further studies to identify the molecular mechanism of CoQ10 on gene expression.
Abstract: The last several decades have revealed clinical and experimental data regarding the importance of magnesium (Mg) in hearing. Increased susceptibility to noise damage, ototoxicity, and auditory hyperexcitability are linked to states of Mg deficiency. Evidence for these processes has come slowly and direct effects have remained elusive because plasma Mg levels do not always correlate with its deficiency. Despite the major progress in the understanding of cochlear mechanical and auditory nerve function, the neurochemical and pharmacologic role of Mg is not clear. The putative mechanism suggests that Mg deficiency may contribute to a metabolic cellular cascade of events. Mg deficiency leads to an increased permeability of the calcium channel in the hair cells with a consequent over influx of calcium, an increased release of glutamate via exocytosis, and over stimulation of NMDA receptors on the auditory nerve. This paper provides a current overview of relevant Mg metabolism and deficiency and its influence on hearing.
Abstract: Magnesium is an essential mineral that is needed for a broad variety of physiological functions. The usual daily magnesium uptake with a western diet is sufficient to avoid deficiency but seems not to be high enough to establish high normal serum magnesium concentrations that are protective against various diseases. Changes in magnesium homeostasis mainly concern the extracellular space, as the intracellular magnesium concentration is well regulated and conserved. The extracellular magnesium concentration is primarily regulated by the kidney, the mechanisms of this regulation have been elucidated recently. Due to the growing knowledge about the regulation of extra- and intracellular magnesium concentrations and the effects of changed extracellular magnesium levels the use of magnesium in therapy gains more widespread attention.
Abstract: Single high oral doses of fluoroquinolones (e.g., 1,200 mg of ofloxacin/kg of body weight) are chondrotoxic in juvenile rats. Characteristic cartilage lesions are detectable as early as 12 h after treatment. Since this dosing regimen does not reflect the therapeutic situation, we studied the effects of a 5- or 7-day treatment with ofloxacin at lower oral doses (10, 30, and 100 mg/kg twice a day [b.i.d.]) on joint cartilage in 4-week-old rats. We additionally investigated whether the effects of ofloxacin under these conditions are enhanced in animals kept on a magnesium-deficient diet during treatment. Knee joints were examined histologically. The concentrations of ofloxacin and magnesium were determined in plasma and cartilage. The lowest ofloxacin dose at which cartilage lesions occurred in animals on a standard diet was 100 mg/kg b.i.d. for 5 days. Peak plasma ofloxacin levels were approximately 10 mg/liter in these rats and thus were in the same range as the levels in the plasma of humans during therapy with high doses of ofloxacin. Treatment with 30 mg of ofloxacin/kg b.i.d. for 7 days caused no cartilage lesions in rats on a standard diet, but lesions did occur in 10 of 12 rats that were simultaneously fed a magnesium-deficient diet. Magnesium concentrations in bone, plasma, and cartilage from animals on an Mg(2+)-deficient diet were significantly lower than those in the controls. The concentration in plasma from animals on an Mg(2+)-deficient diet was 0.27 +/- 0.03 mmol/liter, whereas it was 0.88 +/- 0.08 mmol/liter in plasma from rats on a standard diet (means +/- standard deviations). Ofloxacin treatment did not change the total magnesium concentrations in tissues, as determined with ashed samples. The incidence of ofloxacin-induced lesions was higher in the magnesium-deficient animals, suggesting a synergistic effect. These results must be taken into account for a benefit-risk evaluation if ofloxacin is considered for use in the pediatric population.
Abstract: The cause of low back pain is heterogeneous, it has been hypothesised that a latent chronic acidosis might contribute to these symptoms. It was tested whether a supplementation with alkaline minerals would influence symptoms in patients with low back pain symptoms. In an open prospective study 82 patients with chronic low back pain received daily 30 g of a lactose based alkaline multimineral supplement (Basica) over a period of 4 weeks in addition to their usual medication. Pain symptoms were quantified with the "Arhus low back pain rating scale" (ARS). Mean ARS dropped highly significant by 49% from 41 to 21 points after 4 weeks supplemention. In 76 out of 82 patients a reduction in ARS was achieved by the supplementation. Total blood buffering capacity was significantly increased from 77.69 +/- 6.79 to 80.16 +/- 5.24 mmol/L (mean +/- SEM, n = 82, p < 0.001) and also blood pH rose from 7.456 +/- 0.007 to 7.470 +/- 0.007 (mean +/- SEM, n = 75, p < 0.05). Only intracellular magnesium increased by 11% while other intracellular minerals were not significantly changed in sublingual tissue as measured with the EXA-test. Plasma concentrations of potassium, calcium, iron, copper, and zinc were within the normal range and not significantly influenced by the supplementation. Plasma magnesium was slightly reduced after the supplemenation (-3%, p < 0.05). The results show that a disturbed acid-base balance may contribute to the symptoms of low back pain. The simple and safe addition of an alkaline multimineral preparate was able to reduce the pain symptoms in these patients with chronic low back pain.
Abstract: Fluoroquinolones can cause tendinitis and tendon rupture. However, toxicological as well as clinical information on quinolone-induced tendopathy is scarce. We performed extensive electron microscopic studies with Achilles tendon specimens from ofloxacin-treated rats. The drug was given at a dose of 1,200 mg/kg (body weight) orally. Juvenile Wistar rats received one or three oral doses each of 1,200 mg of ofloxacin/kg (body weight)/day. Three days after treatment, the tenocytes of their Achilles tendons showed degenerative alterations, such as multiple vacuoles and vesicles in the cytoplasm that had developed due to swellings and dilatations of cell organelles. Other indications of cell degradation were the occurrence of cell debris and cell detachment from the extracellular matrix accompanied by a loss of cell-matrix interaction. The tenocytes of juvenile Wistar rats that had been treated at day 36 with a single oral dose of 1,200 mg of ofloxacin/kg (body weight) and sacrificed either 3 or 6 months later exhibited similar degenerative alterations. The number of degenerative alterations of tenocytes after ofloxacin treatment was considerably higher in rats that had received a magnesium-deficient diet than in rats with normal magnesium status. Of the adult rats that had been treated once, 5 times, and 10 times with ofloxacin and killed 1 day later, only those with the 10-times treatment showed a significantly increased number of degeneratively altered tenocytes. In summary, effects observed in tendons show similar pathological features as described earlier in cartilage, indicating that quinolone-induced arthropathy and quinolone-induced tendopathy probably are different clinical manifestations of the same toxic effect on cellular components of connective tissue structures.
Abstract: Net Mg(2+) absorption from the rumen is mainly mediated by a transcellular pathway, with the greater part (62%) being electrically silent. To investigate this component of Mg(2+) transport, experiments were performed with isolated ruminal epithelial cells (REC). Using the fluorescent indicators mag-fura 2, sodium-binding benzofuran isophthalate, and 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, we measured the intracellular free Mg(2+) concentration ([Mg(2+)](i)), the intracellular Na(+) concentration ([Na(+)](i)), and the intracellular pH (pH(i)) of REC under basal conditions, after stimulation with butyrate and HCO(-)(3), and after changing the transmembrane chemical gradients for Mg(2+), H(+), and Na(+). REC had a mean resting pH(i) of 6.83 +/- 0.1, [Mg(2+)](i) was 0.56 +/- 0. 14 mM, and [Na(+)](i) was 18.95 +/- 3.9 mM. Exposure to both HCO(-)(3) and HCO(-)(3)/butyrate led to a stimulation of Mg(2+) influx that amounted to 27.7 +/- 5 and 29 +/- 10.6 microM/min, respectively, compared with 15 +/- 1 microM/min in control solution. The increase of [Mg(2+)](i) was dependent on extracellular Mg(2+) concentration ([Mg(2+)](e)). Regulation of pH(i) has been demonstrated to be Na(+) dependent and is performed, for the most part, by a Na(+)/H(+) exchanger. The recovery of pH(i) was fully blocked in nominally Na(+)-free media, even if [Mg(2+)](e) was stepwise increased from 0 to 7.5 mM. However, an increase of [Mg(2+)](i) was observed after reversing the transmembrane Na(+) gradient. This rise in [Mg(2+)](i) was pH independent, K(+) insensitive, dependent on [Mg(2+)](e), imipramine and quinidine sensitive, and accompanied by a decrease of [Na(+)](i). The results are consistent with the existence of a Na(+)/Mg(2+) exchanger in the cell membrane of REC. The coupling between butyrate, CO(2)/HCO(-)(3), and Mg(2+) transport may be mediated by another mechanism, perhaps by cotransport of Mg(2+) and HCO(-)(3).
Abstract: The cardiovascular risk increases with decreasing serum levels of magnesium, and this already at concentrations within the previous reference range (0.70-1.10 mmol/L). For this reason, the Society for Magnesium Research has updated its 1986 recommendations for the diagnosis of magnesium deficiency. The diagnosis is based on the patient's history, his clinical symptoms, and the results of clinical-chemical investigations of plasma/serum and urine. Further diagnostic methods used include the determination of ionized serum magnesium and the magnesium retention test. The optimal serum magnesium concentration is > 0.80 mmol/L.
Abstract: Quinolone-induced chondrotoxicity is possibly associated with the magnesium-chelating properties of quinolones. This toxic effect seems to be restricted to a rather short time period during postnatal development as shown in rats and dogs. We studied developmental changes of the integrin pattern on canine chondrocytes (e.g. the alpha(v)beta(3)- or alpha(5)beta(1)-integrin), because integrin function depends on divalent cations, as well as the matrix composition (e.g., collagen type II, fibronectin), in 11-, 18-, and 55-week-old Beagles (n=8) by immunohistochemistry. We also analyzed the magnesium and calcium content by atomic absorption spectroscopy in cartilage and bone and studied the effects of a magnesium-deficient diet on joint cartilage in four immature Beagles (18 weeks old at necropsy). The dogs were fed the magnesium-deficient diet for 40 to 46 days. All dogs exhibited gait alterations ('limping') after 4 weeks on the magnesium-deficient diet. Male, magnesium-deficient dogs exhibited pronounced weakness in their front legs; in one of these dogs the front legs were hyperextended to a 90 degrees angle. We observed no significant differences in the integrin pattern in samples from dogs at different developmental stages or in magnesium-deficient dogs in comparison to age-matched controls. Localization of fibronectin in the joint cartilage was found to vary with the age of the dogs as well as with the site of collection. In the middle zone of immature joint cartilage, corresponding to the predilective site of quinolone-induced cartilage lesions, we observed a slight increase in staining with the fibronectin antibody in some samples from magnesium-deficient dogs. Electron microscopy revealed alterations in chondrocytes from the magnesium-deficient dogs (e.g., swollen mitochondria and enlarged endoplasmic reticulum) which are also seen after treatment with quinolones. In summary, we found no significant differences of the integrin pattern on chondrocytes from joint cartilage of dogs at various developmental stages. However, magnesium deficiency in immature dogs induced similar clinical symptoms as quinolone treatment as well as distinct alterations in chondrocytic fibronectin staining and their ultrastructure. This corroborates our findings in rats where magnesium chelation is an important event in quinolone-induced chondrotoxicity.
Abstract: Severe Mg deficiency changed mineral homeostasis, induced membrane damage, increased lipid peroxidation and cytokine concentrations, and reduced immunocompetence. In order to investigate whether the pathobiochemical effects correlate directly with the degree of Mg deficiency or whether there might be a threshold with no detectable effects above, diets with 70, 110, 208, 330 and 850 ppm Mg were fed to growing Wistar rats. After feeding the diets for 0, 10, 20 and 30 days parameters of free radical action (malondialdehyde and vitamin E content), mineral content (Mg, Ca, Fe) in various tissues (liver, spleen, heart, kidney, muscle) and plasma parameters (Mg, Ca, Fe, alanine- and aspartate-aminotransferase) were measured. After 30 days 6-keto-prostaglandin F1 alpha, thromboxane B2, tumor necrosis factor-alpha, and immunoglobulins (IgG, IgM, IgA) were additionally analyzed. Tissue Mg content was either unchanged or only slightly reduced in severe Mg deficiency. Tissue Fe content rose when the extracellular Mg concentration was below 0.25 mM. There was a close positive correlation between tissue Fe and malondialdehyde content, and malondialdehyde was negatively correlated with vitamin E content. Below a threshold of about 0.25 mM plasma Mg concentration, transaminases increased in plasma. The same threshold could be observed for the increase of tissue Ca content, except in the kidney where calcifications were found already in mild Mg deficiency. Tumor necrosis factor-alpha and 6-keto-prostaglandin F1 alpha were increased when the plasma Mg concentration was below 0.15 mM, and thromboxane B2 was increased when plasma was lower than 0.25 mM. IgG and IgA were significantly reduced below 0.25 mM plasma Mg and IgM below 0.4 mM plasma Mg. Mild Mg deficiency, therefore, can be compensated and might not lead to pathological symptoms if not combined with other pathobiological conditions.
Abstract: Quinolone-induced arthropathy is probably caused by a lack of functionally available magnesium in immature joint cartilage. We used an in vitro assay to study the effects of fluoroquinolones on cartilage formation in mouse limb buds from 12-day-old mouse embryos in regular and in magnesium-deficient medium. Omission of magnesium from the medium had no adverse effect on the outcome of the culture: limb buds grew and differentiated well in regular and in magnesium-deficient Bigger's medium. Lack of calcium, however, severely impaired the development of the explants; this result was even more enhanced when both minerals (magnesium and calcium) were omitted. Electron microscopy revealed cell necrosis and deposition of electron-dense material in the vicinity of chondrocytes from limb buds after 6 days in a magnesium-free medium. A series of seven fluoroquinolones was tested at 30, 60, and 100 mg/l medium. At a concentration of 30 mg/l sparfloxacin only had a slight effect on limb development. At concentrations of 60 and 100 mg/l sparfloxacin, temafloxacin and ciprofloxacin impaired limb development in vitro concentration-dependently. The effects were enhanced in a magnesium-deficient medium (concentration of magnesium <10 micromol/l). Fleroxacin, lomefloxacin and ofloxacin impaired limb development only slightly; no significant differences were recognizable between the outcome in regular and in magnesium-deficient medium. Pefloxacin did not show any effect on limb development in both media. Using electron microscopy, very similar alterations as described above for the limbs cultured in magnesium-deficient medium were observed with ofloxacin at a concentration of 30 mg/l, which had no effect on the growth of the explants when evaluated macroscopically. The affinity of six fluoroquinolones to magnesium was determined by the use of a fluorescence assay. The affinity to magnesium correlated with the activity of the drugs in the limb bud assay. We conclude that fluoroquinolones have no effect on murine limb development in vitro at concentrations that are achieved under therapeutic conditions (peak concentrations approx. 1-5 mg/l in plasma). Effects at higher concentrations (60 and 100 mg/l) are slightly enhanced (factor 2) if the magnesium concentration in the medium is low. Macroscopically, limbs develop regularly in a magnesium-free medium, but ultrastructurally typical alterations are exhibited (e.g. cell necrosis and pericellular deposition of electron-dense material).
Abstract: Fluoroquinolones are known for their ability to form chelate complexes with magnesium. Cartilage lesions observed in juvenile animals after quinolone treatment very probably are a consequence of the lack of functionally available magnesium. In cartilage, which contains high amounts of negatively charged proteoglycans, a Donnan distribution can be expected leading to an inhomogeneous distribution of ions (such as magnesium), which may support the toxic effects of magnesium deficiency or quinolone treatment of cartilage. We performed in vitro experiments using dialysis tubes to simulate the unequal distribution of proteoglycans in cartilage and measured the distribution of magnesium, calcium and ofloxacin. We found that the concentration of free magnesium is significantly reduced with the chondroitin sulphate-free solution due to a Donnan effect. For example, using a 3% chondroitin sulphate solution (outside the tubing) dialysed against a chondroitin sulphate-free solution (inside the tubing) the magnesium concentration decreased by 24% from 0.55 +/- 0.02 to 0.42 +/- 0.04 mmol/l inside the tubing during 48 h observation (P < 0.01). Under physiological conditions this unequal distribution of magnesium probably will be much more pronounced because chondroitin sulphate concentrations in cartilage are higher; nevertheless, magnesium concentration is sufficient for regular function of the tissue. During the sensitive phase of quinolone toxicity, magnesium in juvenile cartilage is lower than at other time points during postnatal development. Moreover, additional complexation by quinolones may further reduce the concentration of functionally available magnesium below the critical level.
Abstract: Quinolone treatment or magnesium deficiency induce identical cartilage lesions in juvenile rats and show additive arthropathogenic effects. It has been shown previously that neither condition is arthropathogenic in 8-week-old rats. Joint cartilage from aged individuals is rather prone to pathological alterations but information on prolonged quinolone treatment and/or dietarily induced magnesium deficiency in aged animals is not available. We treated magnesium-deficient (n = 9) aged Wistar rats (age 15 months) and age-matched controls with daily doses of 600 mg ofloxacin/kg body wt. by gastric intubation for 28 days. Further groups of magnesium-deficient and control rats (n = 9 and n = 10, respectively) received the vehicle only. Peak plasma concentrations of ofloxacin in adult rats were 20.5 +/- 5.6 mg/l (mean +/- SD) following treatment with a single dose of 600 mg/kg body wt. At the end of the experiment the degree of magnesium deficiency was most pronounced in plasma (Mg2+-def., 0.33 +/- 0.12 mmol/l; control, 0.97 +/- 0.08 mmol/l) and less pronounced in sternal cartilage (Mg2+-def., 10.8 +/- 3.6 mmol/kg dry wt; control, 13.3 +/- 2.8 mmol/kg dry wt), whereas the magnesium concentration in femoral bone remained unchanged (Mg2+-def., 201 +/- 13 mmol/kg dry wt; control, 204 +/- 11 mmol/kg dry wt). Histological investigation of the knee joints revealed no cartilage lesions following ofloxacin treatment, magnesium deficiency or a combination of both conditions. By contrast, cartilage lesions such as scars and erosions of the joint surface, chondrocyte clusters within acellular areas of the cartilage matrix and persisting clefts were detectable in knee joints from 7 of 10 adult rats (age 9 months) which had been treated with 4 x 600 mg fleroxacin/kg body wt. at 5 weeks of age. Mean plasma concentration of fleroxacin in juvenile rats was approx. 50 mg/l between 1.5 and 6 h after dosing and the drug was still detectable in plasma 48 h after dosing (0.4 +/- 0.1 mg/l). Our data indicate that joint cartilage in aged rats is not altered by a 4-week quinolone treatment, even during magnesium deficiency. Cartilage lesions in adult rats were only detectable if the animals had been treated during the sensitive phase at 5 weeks postnatally.
Abstract: Quinolone-induced arthropathy has been described in juvenile rats between 3 and 6 weeks of age, but not in adult rats. The mechanism of this chondrotoxic effect is probably related to the Mg2+-chelating properties of the drugs, since identical cartilage lesions were observed in magnesium-deficient juvenile rats without quinolone treatment. However, the reasons for the phase-specificity of the effect are unknown. In the present study, we fed a magnesium-deficient diet to Wistar rats at different postnatal developmental stages. Cartilage lesions were only observed in magnesium-deficient rats between 3 and 5 weeks of age, but not in rats receiving the magnesium-deficient diet during weeks 5 to 8, weeks 8 to 11, or months 15 to 16. The formation of cartilage lesions was not related to the magnesium concentration in plasma, since magnesium concentrations in plasma were similarly reduced in rats with and without cartilage lesions. However, chondrotoxicity correlated with magnesium content in articular cartilage. In articular cartilage (articular and epiphyseal cartilage in immature rats) and bone, magnesium content was more reduced in rats receiving the magnesium-deficient diet between 3 and 5 weeks of age as compared with rats receiving the magnesium-deficient diet during weeks 8 to 11 postnatally. It was not possible to reduce the magnesium content in bone tissue of 15-month-old Wistar rats, which suggests a lower magnesium turnover in aged rats. Magnesium content in epiphyseal cartilage of 2-week-old rats (total femoral head) was 41.9 +/- 16.9 mmol/kg dry weight. The magnesium content in joint hyaline cartilage was significantly lower in 4-week-old rats (19.5 +/- 3.6 mmol/kg dry weight) and increased subsequently again to 48.5 +/- 9.2 mmol/kg dry weight (mean +/- SD; n = 8 to 16). Increase of the magnesium content in femoral bone between weeks 4 and 6 postnatally was less pronounced (139 +/- 10 and 175 +/- 15 mmol/kg dry weight, respectively). Taken together, these data show that in 4-week-old rats, magnesium concentration in joint hyaline cartilage is significantly lower than at other times during postnatal development. Only at this developmental stage can cartilage lesions be induced by feeding rats a magnesium-deficient diet. This period correlates well with the sensitive phase of immature rats toward the chondrotoxic action of quinolones.
Abstract: The study investigated the influence of prolonged physical stress during survival training with food and fluid deprivation on the serum concentrations of erythropoietin (EPO). A group of 29 male subjects [mean age 22.2 (SD 2.8) years, height 1.78 (SD 0.06) m, and body mass (m(b)) 73.5 (SD 8.6) kg] were studied for 5 days of multifactorial stress including restricted water intake (11 H2O. day(-1)) and food intake (628 kJ. day(-1)) combined with physical exercise (estimated energy expenditure approximately 24000 kJ.day(-1)) and sleep deprivation (20 h within 5 days). Blood samples were taken before (T1), after 72 h (T2) and 120 h (T3) of physical stress, and after 48 h, (T4) and 72 h (T5) of recovery. The samples were analysed for EPO, and concentrations of serum iron (Fe), haptoglobin (Hapto), transferrin (Trans), ferritin (Fer), haemoglobin (Hb) and packed cell volume (PCV). The m(b) had decreased by 6.77 kg at T3 (P <0.01) and 0.68 kg at T5. The EPO and Hapto decreased during the survival training (P <0.01) and increased during the recovery period (P <0.01). The Fe increased during the survival training (P <0.01) and remained above the control concentrations during recovery (P <0.01). The Hapto decreased during the survival training (P <0.01) and remained below control concentration at T4 and T5 (P <0.01). The Trans decreased continuously over the week (P <0.01). The Fer increased during the survival training (P <0.01) and returned to control concentration at T5. The Hb increased from T1 to T2 (P <0.01) and had decreased significantly at T5 (P <0.01). The PCV increased from T1 to T2 (P <0.01) and remained below control levels afterwards (P <0.01). From our study it was concluded that, in humans, prolonged physical stress with food and fluid deprivation induces a marked EPO decrease, which is followed by a rapid increase during recovery to restore the reduced O2 transport capacity.
Abstract: Male Wistar rats were fed diets with different Mg content, ranging from 70 to 850 ppm Mg, for 30 days. After 0, 10, 20 and 30 days, some of the rats were sacrificed for measuring weight, lipid peroxidation, Fe, vitamin E, Na+, K+, Mg2+ and Ca2+ content of testes. After 30 days, the morphology of the testes was investigated by electron microscopy. Mg deficiency induced an increase in weight, Na+, Ca2+ and Fe content and a reduction of K+ and Mg2+ content. Vitamin E content was reduced and the content of malondialdehyde as an indicator of lipid peroxidation was increased. Mg deficiency induced morphological alterations in up to 40% of the spermatids in the 70 ppm Mg group, which consisted: 1) in injured stretching of spermatids; 2) in an irregular arrangement of coarse fibres with missing microtubulus complex (axoneme) and microtubulus sheath; 3) in the development of up to 4 bundles of outer fibrils in one spermatid. The increase of Fe content, lipid peroxidation and the onset of morphological alterations occurred already at a mild degree of Mg deficiency.
Abstract: Male Wistar rats were intraperitoneally injected twice with 0.4 mmol kg-1 FeSO4. One, 2 and 4 days after the second Fe injection, Fe and malondialdehyde (MDA) content in testis was measured, the morphology studied by light and electron microscopy and the number of spermatids counted. After Fe injection, Fe and MDA content had increased in parallel. Light microscopic inspection on days 1 and 2 after Fe injection revealed numerous necroses in the different cell types of the germ epithelium. Four days after Fe injection, fewer alterations were found. Electron microscopic investigations revealed that some spermatids contained up to three nuclei and at least three axonemes. In some sperm tails up to 11 axonemes were found. In some midpieces two or three complexes of axonemes, outer dense fibres and mitochondria were observed. In other midpieces axonemes were absent and replaced by granular and filamentous material. The number of spermatids was reduced 4 days after Fe treatment. The increase in the number of axonemes was similar to that seen in Mg and Zn deficiency, indicating that the increase in Fe content and oxygen free radicals is the major reason for the biochemical and morphological alterations in Mg and Zn deficiency.
Abstract: Recently, we showed that magnesium deficiency induces lesions in knee joint cartilage from 5-week-old rats that are very similar to ofloxacin-induced cartilage defects. We concluded that quinolone-induced arthropathy is probably due to chelation of magnesium and thus a deficit in functionally available magnesium in joint cartilage (Stahlmann et al. 1995). As magnesium deficiency in joint cartilage could impair chondrocyte-matrix interaction which is mediated by cation-dependent integrin receptors of the beta 1-subfamily, we investigated integrin expression in joint cartilage from untreated, ofloxacin-treated and magnesium-deficient Wistar rats. With immunohistochemical methods using monoclonal and polyclonal antibodies, we showed that the integrin pattern in joint cartilage from rats corresponded largely to integrin expression described for human cartilage tissue: beta 1, alpha 1, alpha 3 and alpha v subunits and the alpha 5 beta 1 and alpha v beta 3 heterodimers were consistently expressed. Joint cartilage lesions were detected in ofloxacin-treated and magnesium-deficient rats. Lesions were more pronounced in the quinolone-treated group. Expression of several integrins was reduced in the vicinity of lesions after oral treatment with 2 x 600 mg ofloxacin/kg for 1 day. Gross-structural lesions (e.g., cleft formation, unmasked collagen fibres) in magnesium-deficient rats were very similar but changes in integrin expression were less pronounced. On the other hand, changes in cartilage matrix composition showed similar alterations in ofloxacin-treated and magnesium-deficient rats: fibronectin deposition in the cartilage matrix increased in both groups while glycosaminoglycan content decreased. In summary, similar defects occur in ofloxacin-treated and magnesium-deficient rats and with immunohistochemical methods subtle differences are demonstrable.
Abstract: Ultrastructural changes in immature articular cartilage were studied after treatment of 5-wk-old rats with ofloxacin-a fluoroquinolone-and in magnesium deficiency. Magnesium deficiency was induced by feeding a magnesium-deficient diet for 9 days; the condition was confirmed by measuring the concentrations of the mineral in plasma, bone, and cartilage samples of the animals by atomic absorption spectrophotometry. Oral administration of single doses of 600 or 1,200 mg ofloxacin/kg body weight and magnesium deficiency were sufficient to induce gross structural cartilage defects. Alterations observed on the ultrastructural level showed striking similarities in magnesium-deficient rats and in rats treated with single doses of 600 mg ofloxacin/kg body weight. Typical observations were (a) bundle-shaped, electron-dense aggregates on the surface and in the cytoplasm of chondrocytes, (b) detachment of the cell membrane from the matrix and necrotic chondrocytes, (c) reduction of the extracellular matrix, and (d) swelling of cell organelles such as mitochondria. These findings further substantiate the histological finding that quinolone treatment and a dietarily induced magnesium-deficiency induce indistinguishable pathological conditions in immature joint cartilage, and they suggest that quinolone-induced arthropathy is probably caused by a reduction of functionally available magnesium (ionized Mg2+) in cartilage (42). Furthermore, they provide a basis for aimed studies with human cartilage samples from quinolone-treated patients that might be available postmortally or after hip replacement surgery.
Abstract: The aim of this study was to investigate fluidregulating mechanisms, with special regard to the role of plasma proteins in the control of plasma volume (PV), and the role of the superficial tissues as a water storage organ of the body during prolonged physical strain. 29 male subjects (mean age 22.2 +/- 2.8 years) were studied during a 5 day period of survival training with multifactorial strain including restricted water intake (11 H2O.day-1) and food intake (628 kJ.day-1) additionally to physical exercise and sleep deprivation (20 h within 5 days). Under field conditions the heart rate was monitored continuously, and body mass, body composition, thickness of the shell tissues, and blood parameters were measured at (T1), after 72 h (T2), after 120 h (T3) and in the recovery period after 48 h (T4) and 72 h (T5). The estimated energy expenditure was approximately 24,000 kJ.day-1. The mean decrease of body mass was 6.77 kg (9.5%) at T3 (p < 0.001), 0.95 kg (1.3%) at T4 (p < 0.05) and 0.68 kg (0.9%) at T5 (n.s.). A reduction of total body water of 3.8 1 was estimated at T3. Serum creatinine ([Cr]) was raised at T3 by 18.5% (p < 0.0001). No relationship was found between [Cr] and other parameters. The PV decreased by 3.7% (p < 0.0001) at T2, increased by 1.6% (p < 0.0001) at T3 and was not different to baseline at T4 (+0.2%; n.s.). Total protein concentration ([TP]) increased at T2 (11.7%; p < 0.0001) and T3 (2.6%; p < 0.01), and decreased (p < 0.0001) at T4 (8.2%) and T5 (5.7%). Plasma proteins shifted into the intravascular space at T2 and T3 and moved out of the intravascular space at T4 and T5. This gives support to the hypothesis that one of the counterregulatory mechanisms maintaining PV during prolonged exercise is provided by protein shifts from the extravascular into the intravascular space. Our data provide evidence that this mechanism assists PV homeostasis efficiently over a period of 120 h with multifactorial strain, even under conditions with a fluid loss of almost 8% of the total body water.
Abstract: Quinolones accumulate in cartilage, and because they form chelate complexes with divalent cations, they possess the potential to induce a deficiency of functionally available magnesium. To test the hypothesis that quinolone-induced arthropathy is caused (or aggravated) by magnesium deficiency in cartilage, we induced magnesium deficiency by feeding juvenile rats a magnesium-deficient diet for 9 days and treated the rats with single oral doses of ofloxacin (0, 100, 300, 600, or 1,200 mg/kg of body weight) during this period. Additional groups of juvenile rats on a normal diet were treated with ofloxacin correspondingly. Typical cartilage lesions (e.g., swollen matrix, cleft formation) were found in knee joints of all magnesium-deficient rats, including those without ofloxacin treatment. Lesions in these groups were not distinguishable from lesions induced by a single dose of 600 mg of ofloxacin per kg of body weight or higher in rats on a normal diet. Ofloxacin levels in plasma after 600 mg/kg of body weight were approximately 10-fold higher than those in humans during therapy with this quinolone. Lesions in rats treated with ofloxacin plus magnesium deficiency were more pronounced than those in rats with normal magnesium concentrations. After intake of a magnesium-deficient diet for 9 days, the magnesium concentration in serum (mean +/- standard deviation) was 0.18 +/- 0.05 mmol/liter (control on normal diet, 0.82 +/- 0.10 mmol/liter). Magnesium concentrations in bone (femur) and cartilage (processus xiphoideus) samples were 64.7 +/- 10.5 and 14.3 +/- 3.9 mmol/kg of dry weight, respectively, which corresponded to approximately 50% of the concentrations measured in controls on a normal diet. It was concluded that quinolone-induced arthropathy is probably caused by a deficit of available magnesium in joint cartilage due to the formation of quinolone-magnesium chelate complexes. If juvenile patients must be treated with quinolones for serious infections, it seems prudent to ensure that these patients do not have a disturbed magnesium balance.
Abstract: Human erythrocytes either untreated or Mg2+(-)loaded by means of A23187 in the presence of 3 or 12 mM MgCl2 were haemolysed by freezing and thawing. In the haemolysates the concentration of total Mg2+ (by atomic absorption spectrophotometry), free Mg2+ (by a Mg2+(-)sensitive electrode) and ATP were determined. The increase in the free Mg2+ concentration was also measured when titrating the haemolysates with MgCl2. The experiments yielded a total Mg2+ buffer capacity of 4.85mM with a Ka of 0.9 mM-1, indicating that 2,3 bisphosphoglycerate was the main Mg2+ buffer in haemolysates of erythrocytes which had been ATP-depleted during preparation. The activity coefficient of free Mg2+ in erythrocytes was the same as in the chloride-based calibration solutions.
Abstract: Rat erythrocytes loaded with Mg2+ plus Na+ performed Mg2+ uptake under an intracellular/extracellular Na+ gradient. Mg2+ uptake was coupled to Na+ release at a stoichiometric ratio of 1 Mg2+/2 Na+.Mg2+ uptake was inhibited by amiloride, imipramine and quinidine. Mn2+ was taken up by the same transporter as Mg2+. Similar results had been found for net Mg2+ efflux via Na+/Mg2+ antiport in such rat erythrocytes. Hence, it can be concluded that Na+/Mg2+ antiport in Mg(2+)-loaded rat erythrocytes operates reversibly according to the direction of the Na+ gradient which is a contributing driving force. Net Mg2+ influx was dependent on ATP which increased the affinity of intracellular Mg2+ by activating Na+/Mg2+ antiport. Mg2+ uptake was increased by phorbol ester and inhibited by staurosporine, indicating that ATP may function via protein phosphorylation by protein kinase C.
Abstract: In primary cultures of rat hepatocytes, the effects of extracellular Mg2+ and Fe on lipid peroxidation (LPO) as measured by means of malondialdehyde (MDA) formation were investigated. Incubation of hepatocytes at decreasing extracellular Mg2+ concentration enhanced LPO, depending on extracellular Fe. About 96% of MDA accumulated in the culture medium. Addition of desferrioxamine prevented LPO. Additionally, the formation of oxygen free radicals was determined by fluorescence reduction of cis-parinaric acid. With this method, an immediate decay of fluorescence was found after addition of Fe2+. Fluorescence reduction was completely prevented by desferrioxamine, indicating the function of extracellular Fe. This mechanism may operate additionally to the increase in intracellular Fe and intracellular formation of oxygen free radicals during Mg deficiency in vivo.
Abstract: The polyamines spermine, spermidine and putrescine interact with Mg(2+)-sensitive macroelectrodes based on the neutral carrier ETH 7025; the interaction in decreasing order being spermine, spermidine and putrescine. The effect is small and dependent on the ionized magnesium concentration ([Mg2+]free), only resulting in a significant increase in the measured [Mg2+]free with spermine and spermidine at [Mg2+]free less than 0.5 mM. The polyamines compete with Mg2+ for common binding sites on Mg2+ buffers such as ATP, ADP and citrate, releasing bound Mg2+ and increasing the [Mg2+]free. This effect is most prominent with Mg ATP and the action of the polyamines in decreasing order is spermine, spermidine and putrescine. Increases in polyamines which occur in cell proliferation and cancer could thus secondarily increase the [Mg2+]free resulting in an activation of Mg(2+)-dependent metabolic pathways.
Abstract: Plasma and erythrocyte Mg2+ concentrations were found to be increased in 14 haemodialysis patients with chronic renal failure and in 7 chronic renal failure patients receiving chronic ambulatory peritoneal dialysis. The rate of Na+/Mg2+ antiport was significantly higher in haemodialysis patients, but not in chronic ambulatory peritoneal dialysis patients (control: 0.15 +/- 0.02, haemodialysis: 0.46 +/- 0.08, chronic ambulatory peritoneal dialysis: 0.21 +/- 0.06; Mg2+, mmol/30 min x 1 cells). High erythrocyte Mg2+ content in chronic renal failure results from the increased plasma Mg2+, which induces elevated Mg2+ uptake during haematopoiesis. An increased rate of Na+/Mg2+ antiport, which only performs Mg2+ efflux, leads to a relatively lower erythrocyte Mg2+ content in haemodialysis patients compared with chronic ambulatory peritoneal dialysis patients. The elevated Na+/Mg2+ antiport in erythrocytes from haemodialysis patients was almost normalised after haemodialysis. Incubation of normal erythrocytes with heat-inactivated plasma from haemodialysis patients led to a doubling of Na+/Mg2+ antiport, indicating the presence of a heat-stable, dialysable plasma factor. This factor does not accumulate in chronic ambulatory peritoneal dialysis patients. After renal transplantation all changed quantities of Mg2+ metabolism returned to normal.
Abstract: Na+/Mg2+ antiport and Na(+)-independent Mg2+ efflux were investigated in erythrocytes of 41 patients with cystic fibrosis and 26 controls. Na(+)-independent Mg2+ efflux was unchanged in cystic fibrosis, but a significantly increased activity of Na+/Mg2+ antiport was detected (control: 0.16 +/- 0.02, cystic fibrosis: 0.39 +/- 0.06, Mg2+ efflux, mmol/30 min x 1 cells, mean +/- SEM, p < 0.01). An increased activity of Na+/Mg2+ antiport was only found in patients with severe clinical symptoms. There was no correlation of the increased Na+/Mg2+ antiport to the dF508 genotype. In a patient with increased Na+/Mg2+ antiport, the capacity of this transport system was unchanged 14 weeks after double lung transplantation but reached control values after 53 weeks. The sweat of cystic fibrosis patients with severe clinical symptoms showed a significantly increased Mg2+ concentration (control (n = 12): 0.053 +/- 0.08, cystic fibrosis (n = 9): 0.123 +/- 0.016 mmol/l, mean +/- SEM, p < 0.001).
Abstract: To ascertain possible interactions of intracellular Mg2+ and Ca2+, the concentration of intracellular free Ca2+ ([Ca2+]i) and intracellular free Mg2+ ([Mg2+]i) were experimentally increased within physiological ranges and it was measured by means of fura-2 and mag-fura-2 whether the increased concentration of one divalent cation affected the concentration of the other. A four-fold increase of [Ca2+]i in rat thymocytes by concanavalin A or thapsigargin had no significant effect on [Mg2+]i. Incubation of rat thymocytes in Na(+)-free medium increased [Mg2+]i from 0.35 to 0.7 mM. This increase in [Mg2+]i did not affect [Ca2+]i or the action of thapsigargin on [Ca2+]i.
Abstract: Hydrogen peroxide destroyed the Na+/Mg2+ antiport in Mg(2+)-loaded human and rat erythrocytes and increased the leakage of intracellular Mg2+ and K+. These effects are opposite to the increase of Na+/Mg2+ antiport and unchanged Na(+)-independent Mg2+ efflux from erythrocytes of patients with cystic fibrosis score 3. Thus, the increase of Na+/Mg2+ antiport in these patients is not caused by increased formation of free radicals.
Abstract: Polyamines, particularly spermine, in physiological concentrations interact with mag-fura-2 and the mag-fura-2/Mg2+ complex, resulting in reduced values of free Mg2+ concentration. Similarly, polyamines interact with ATP and MgATP. Thus, free Mg2+ concentration, as measured by 31P-NMR or mag-fura-2, is underestimated in the presence of polyamines, particularly of spermine.
Abstract: The time course of malondialdehyde (MDA), Fe, vitamin E, superoxide dismutase (Cu, Zn-SOD) and glutathione peroxidase (GSH-Px) was measured in serum, liver, kidney and heart from rats between day 17 of gestation and day 20 after birth. MDA was higher in fetal than maternal tissues and showed a transient increase after birth. The low maternal MDA levels were reached later than 3 weeks after birth. Fe was higher in fetal than in maternal serum and liver. Five days after birth Fe drastically dropped in these tissues. The antioxidant factors vitamin E, Cu, Zn-SOD and GSH-Px were low in fetal tissues and rose after birth. It is discussed whether lipid peroxidation is increased in fetal tissues because of less-developed antioxidant defence mechanisms.
Abstract: Isolated mesenchymal limb bud cells from day-12 mouse embryos grown at high density in organoid culture at the medium/air interphase differentiate into chondrocytes and form cartilage nodules. Upon addition of beta-glycerophosphate (beta-GP), cartilage undergoes endochondral mineralization. This beta-GP-induced mineralization was investigated by measuring the calcium content in the cultures and the activity of alkaline phosphatase (AP) in the cell mass and the medium. Calcium incorporation depended on the amount of beta-GP added. After continuous treatment, mineralization began on day 8 of the culture period and increased linearly until day 15. In long-term cultures, periodical treatment for 6 days caused an increase in mineralization the older the cultures were, but the slope of increase was proportionately less steep. Treatment at the latest period on days 19-24 resulted in a markedly reduced mineralization. After short-term treatment (48 hours), mineralization increased also the older the cultures were and proceeded during further cultivation in beta-GP-free medium. This kinetic behavior indicates a dependency of mineralization on cartilage maturation in this in vitro system. AP activity increased enormously and nearly logarithmically in the cell mass in beta-GP-free medium, whereas beta-GP treatment inhibited this drastic increase. In the medium, considerable activities of AP were also measurable from day 10 onward. It increased in beta-GP-free medium up to day 14, but was diminished after mineralization had been induced. Levamisole inhibited AP activity dose dependently when added directly to the enzyme-containing medium (100% inhibition at 10(-3) M).(ABSTRACT TRUNCATED AT 250 WORDS)
Abstract: In patients with cystic fibrosis plasma concentrations of Zn and Mg were unchanged, plasma Ca concentrations were somewhat decreased, but plasma Fe concentrations were drastically reduced; the ratio Cu/Fe in plasma was increased. The Mg and Zn contents of erythrocytes from patients were unchanged. Therefore, the Mg and Zn content of erythrocytes cannot serve for the detection of patients with cystic fibrosis and their heterozygotes, as has been suggested. Cl(-)-dependent Mg2+ efflux from Mg(2+)-loaded erythrocytes was not affected in cystic fibrosis. Na(+)-dependent Mg2+ efflux was increased only in erythrocytes from patients with the most severe clinical symptoms.
Abstract: The effects of a low zinc status on selenium metabolism were investigated in female and male rats which were fed diets with low and adequate zinc contents and a suboptimal selenium content. For the selenium content and glutathione peroxidase activity in the liver and plasma of the female animals no differences were found between the low zinc group and the pair-fed zinc-adequate control group. In the male rats zinc depletion resulted in testis atrophy and decreased testicular contents of selenium and glutathione peroxidase. In the pair-fed and ad libitum-fed control groups the levels of hepatic selenium and glutathione peroxidase and plasma glutathione peroxidase in the males were lower than those in the females. In the low zinc group, however, they rose to the levels of the females. The results indicate that these effects of zinc deficiency on selenium metabolism are sex-specific and suggest that they are related to changes in the sex hormone status of the male animals.
Abstract: Isoproterenol increased the Mg2+ content of hepatocytes after injection into rats or after addition to collagenase-dispersed hepatocytes. cAMP also the increased cellular Mg2+ content of isolated hepatocytes. This effect was prevented by staurosporine. Phorbol ester had no effect on the Mg2+ content of isolated hepatocytes, and after injection of isoproterenol into rats, protein kinase C of liver was not affected. It was concluded that isoproterenol induced long-term Mg2+ influx via the activation of protein kinase A which can be inhibited by staurosporine.
Abstract: Mg2+ efflux from Mg(2+)-loaded rat thymocytes was stimulated by 0.1 mM dibutyryl cAMP (db cAMP). The activation of Mg2+ efflux by db cAMP was more expressed at lower Mg(2+)-loading. cAMP induced only a very small increase in the concentration of intracellular free Mg2+ which cannot explain the activation of Na+/Mg2+ antiport. From these results it was concluded that cAMP increases the affinity of the Na+/Mg2+ antiporter for intracellular Mg2+, probably by phosphorylation.
Abstract: Female Wistar rats received an oral dose of 700 mg salicylic acid/kg body wt., given as sodium salicylate. Some of the salicylate-treated rats received two subcutaneous injections of 100 mumol kg-1 ZnCl2 (24 h before and simultaneously with the salicylate administration). Other animals were given one subcutaneous injection of 100 mumol kg-1 ZnCl2 simultaneously with the salicylate treatment. Control rats were similarly injected with ZnCl2. Twenty four hours after salicylate treatment, serum and livers were taken for histochemical and biochemical analysis. The most remarkable effects of the treatment were enrichment of lipid droplets and iron and a reduction of glycogen, particularly in the periportal hepatocytes. The effects of salicylate were partially prevented by two ZnCl2 injections. The protective effects of ZnCl2 may be due to lower iron uptake into hepatocytes and by the induction of zinc metallothionein, which can serve as a scavenger for oxygen radicals.
Abstract: Mg(2+)-depleted rat reticulocytes reincubated in Mg(2+)-containing media expressed net Mg2+ influx, which was the same in NaCl, choline Cl and sucrose medium. Km of Mg2+ influx amounted to 1.2 mM and Vmax to 0.9 mmol/l cells x h. Mg2+ influx into reticulocytes was inhibited by amiloride, quinidine and imipramine. Mg2+ uptake together with Cl- for charge compensation could be excluded. However, the cation which must be exchanged for Mg2+ in Mg2+ uptake could not be identified because of the low rate of Mg2+ influx.
Abstract: Control rats and rats pretreated with two i.p. injections of 15 mg/kg Fe, given as FeCl3, received either one oral dose of 700 mg/kg salicylic acid, given as Na salicylate, or 100 mumol ZnCl2/kg s.c., or salicylate and ZnCl2. In the rats given Fe this treatment was simultaneous with the second iron injection. Salicylate and Fe alone caused a small increase in lipid peroxidation (LPO) measured as malondialdehyde formation in the liver by means of the thiobarbiturate method. When given together, however, Fe and salicylate caused a drastic increase of LPO in liver, which was reduced by the simultaneous injection of ZnCl2. Hepatotoxicity as determined histochemically by lipid storage paralleled LPO. The protective effect of Zn on LPO and hepatotoxicity was not correlated to metallothionein induction in liver. The protective effect of Zn can be explained by the competition of Fe with Zn for binding to salicylate which reduces Fe-salicylate-induced LPO and hepatotoxicity.
Abstract: Na(+)-dependent Mg2+ efflux from Mg2(+)-loaded rat erythrocytes was determined from the increase of extracellular Mg2+ concentration or decrease of intracellular Mg2+ content, as measured by means of atomic absorption spectrophotometry. Mg2+ efflux was specifically combined with the uptake of Na+ at a stoichiometric ratio of 2Na+:1Mg2+, indicating electroneutral Na+/Mg2+ antiport. Na+/Mg2+ antiport depended on intracellular ATP and was inhibited by amiloride and quinidine, but was insensitive to strophanthin. Net Mg2+ efflux was only occurring at increased concentration of intracellular Mg2+ ([Mg2+]i), and stopped when the physiological Mg2+ content was reached. Intracellular Mg2+ acted cooperatively with a Hill coefficient of 2.4, which may indicate gating of Na+/Mg2+ antiport at increased [Mg2+]i. At increased intracellular Na+ concentration, Na+ competed with intracellular Mg2+ for Mg2+ efflux and Na+ could leave the rat erythrocyte via this transport system. Na+/Mg2+ antiport was working asymmetrically with respect to extra- and intracellular Na+ and Mg2+, and did not perform net Mg2+ uptake.
Abstract: Mg2(+)-loaded rat erythrocytes performed Mn2+/Mg2+ antiport, which was nonspecifically stimulated by anions and cations. Mn2+/Mg2+ antiport was shown to operate via the Na+/Mg2+ antiporter because extracellular Na+ and Mn2+ inhibited the intracellular uptake of each other's ions competitively. Furthermore, Mn2+/Mg2+ antiport and Na+/Mg2+ antiport were identically inhibited by various amiloride derivatives. Na+/Mg2+ antiport of chicken and human erythrocytes cannot perform Mn2+/Mg2+ antiport although chicken erythrocytes took up more Mn2+ than rat erythrocytes.
Abstract: Chicken erythrocytes preloaded with Mg2+ exchange one extracellular Mn2+ for two intracellular H+. Chicken erythrocytes preloaded with Mn2+ alone or with Mg2+ plus Mn2+ performed efflux of Mn2+, which was higher at pH 6 than at pH 7.4, indicating reversibility of Mn2+/H+ antiport. Mn2+/H+ antiport was not inhibited by 1 mM KCN plus 1 mM iodoacetic acid or 1 mM amiloride. Mn2+ influx was activated by anions. Mn2+ efflux via Mn2+/H+ antiport was inhibited by competition between H+ and K+.
Abstract: Na(+)-independent Mg2+ efflux from Mg2(+)-loaded human, rat and chicken erythrocytes was reduced by extracellular Cl-. Na(+)-independent Mg2+ efflux at low extracellular Cl- concentration (sucrose medium) was inhibited by SITS and was nearly insensitive to SITS in 150 mM choline Cl medium. The inhibition of Mg2+ efflux by extracellular Cl- and DIDS could be overcome by the lipophilic permeant tetraphenylphosphonium cation. Na(+)-independent Mg2+ efflux from human and rat erythrocytes in sucrose and choline Cl medium was inhibited by cAMP and by amiloride and amiloride analogues. The results indicate that Na(+)-independent Mg2+ efflux in high Cl- medium is performed by a similar or the same Mg2+ efflux system, operating in sucrose medium in which the efflux of Mg2+ is accompanied by the efflux of Cl- for charge compensation.
Abstract: Mg(2+)-loaded rat thymocytes and HL 60 (human promyelocytic leukemia) cells expressed a high rate of Na(+)-dependent net Mg2+ efflux which was inhibited by two thirds by 1 mM amiloride. During net Mg2+ efflux, extracellular Na+ was taken up at a stoichiometric ratio of 2 Na+ to 1 Mg2+, indicating electroneutral Na+/Mg2+ antiport as found for erythrocytes. Na(+)-independent Mg2+ efflux was not significantly expressed in these cell types.
Abstract: Pregnant Wistar rats were treated with 5 oral doses of 100 or 300 mg/kg salicylic acid from day 16 to 20 of gestation. At day 21 of gestation, copper concentrations were measured in serum, liver and cell organelles of liver from dams and litters after cell fractionation. Salicylate caused a reduction of maternal serum Cu and an increase in fetal liver Cu. The increase of Cu in fetal liver was proportional to the Cu content of the organelles. It was concluded that salicylate bound Cu and transferred Cu from maternal serum to the fetus. The increase in fetal liver Cu was explained by displacement of Zn from Zn-metallothionein by Cu, because Zn-metallothionein is high in fetal liver and Cu has a higher affinity to metallothionein than Zn. Such a mechanism was not significant in maternal liver because of the low Zn-metallothionein content in maternal liver.
Abstract: One day after oral application of 700 mg (5.5 mmol)/kg salicylic acid given as Na salicylate, hearing thresholds in rats, measured by acoustically evoked responses at 10 and 20 kHz, were increased. Salicylate-induced hearing loss was completely prevented by simultaneous s.c. injection of 6 mg (92 mumol)/kg Zn, whereas simultaneous s.c. injection of 1.5 mmol/kg MgCl2 had no effect. Simultaneous s.c. injection of 100 mg (152 mumol)/kg desferrioxamine had only a minor beneficial effect indicating that salicylate-induced Fe accumulation plays no significant role in salicylate ototoxicity.
Abstract: The presence of the low molecular weight protein metallothionein (MT) has been investigated in fetal forelimbs, brain and liver from the mouse with the aim of using the protein as a biochemical marker for the early recognition of potential teratogenic agents in the future. Forelimbs, brain and liver were taken from mouse fetuses at ages ranging from 12 to 18 d. Each type of organ was homogenized and centrifuged at 9000 x g. The analysis of MT in the supernatants (S9) with the Cd-heme saturation method detected in all three cases the presence of a low molecular weight, Cd-binding protein whose concentration increased with the age of the fetus. Analysis of the S9 fractions using gel- and anion exchange-chromatography and polyacrylamide gel electrophoresis demonstrated the existence of a protein analogue to the hepatic MT in forelimbs and brain.
Abstract: Application of salicylate increased the concentration of metallothionein (MT) in liver of pregnant rats as well as of adult male rats, whereas in fetal liver, MT was reduced by salicylate. Induction of MT synthesis by salicylate is an indirect effect because in cultured hepatocytes salicylate did not induce MT synthesis. Salicylate increased MT also in adrenalectomized rats. Indomethacin induced the same concentration of MT in maternal liver as salicylate. However, indomethacin had no effect on MT in fetal liver. Induction of MT in adult liver by salicylate and indomethacin was independent of zinc.
Abstract: Net Mg2+ efflux from Mg2+-loaded human erythrocytes was maximal after reincubation in sucrose. Net Mg2+ efflux was not inhibited by furosemide or bumetanide and, therefore, was not performed by the (Na,K,Cl)- or (K,Cl)-cotransport system. A component of net Mg2+ efflux was inhibited by extracellular NaC1, KCl, LiCl, choline Cl and SITS, in analogy to the inhibition of net Cl- and SITS. Therefore, it was concluded that net Mg2+ efflux is dependent on net Cl- efflux for charge compensation. Cl- -dependent net Mg2+ efflux was inhibited by amiloride. Only 10% of the maximal net Mg2+ efflux may depend on extracellular Na+.
Abstract: One of each pair of female sister rats aging 1, 4, 7 or 10 months was exposed during 3 months to 31.5 mg/L Cd (as CdCl2) in its drinking water and sacrificed immediately after Cd exposure together with its untreated sister. Concentrations of Cd, Zn and Cu were measured in the kidneys (medulla and cortex), the liver, the duodenum and the uterus. Furthermore, the subcellular distribution of Cd was measured in renal tissue. The accumulation of metal ions, defined as the difference between Cd-treated and untreated rats, was pronounced in all tissues except the uterus and was significantly decreased at increasing age. Multivariate analysis of variance revealed significant interaction with Zn and Cu. Higher Cd accumulation in the tissues of young animals probably depends on the higher consumption of contaminated drinking water per kilogram of body weight. High concentrations of Cd detected in cell nuclei may be due to the similarity between Cd2+ and Ca2+.
Abstract: Net Mg2+ efflux from Mg2+-loaded, human, rat and chicken erythrocytes was measured in sucrose, NaCl and choline Cl medium. Thus, Na+-dependent (NaCl minus choline Cl) and Na+-independent Mg2+ efflux (in sucrose) were determined. Na+-dependent Mg2+ efflux amounted to 0.16, 8.9 and 1.57 mmol/l cells x 30 min, Na+-independent Mg2+ efflux amounted to 0.89, 1.55 and 0.37 mmol/l cells x 30 min for human, rat and chicken erythrocytes. Na+-dependent Mg2+ efflux was inhibited by quinidine. Na+-independent Mg2+ efflux was inhibited by SITS and Cl-. A small fraction of Na+-independent Mg2+ efflux (in choline Cl) was resistant to SITS and Cl-. Ca2+ loading increased Mg2+ efflux similar to K+ efflux (Gardos effect). This effect was differently expressed in human and chicken erythrocytes.
Abstract: Pregnant and non pregnant rats were fed diets with different Mg content and treated with 5 oral doses of 300 mg/kg salicylic acid for 5 consecutive days or from day 16 to 20 of gestation. One day after the final dosage, serum Mg and Ca concentrations were measured by atomic absorption spectrophotometry. In maternal rats, salicylate caused a strong decrease of serum Ca with increasing serum Mg concentrations (r = -0.8706). In fetal and nonpregnant adult female rats, serum Ca was not significantly decreased by salicylate with increasing serum Mg concentrations. However, the hypocalcemic effect of salicylate was found when nonpregnant young growing rats were fed a Ca-deficient diet.
Abstract: In rats, Mg deficiency caused a moderate hearing loss, measured by means of evoked potentials at 10 and 20 kHz, which was repaired after refeeding a normal diet. Application of 700 mg/kg salicylic acid or injection of 5 x 100 mg/kg gentamicin also caused a reversible hearing loss in normally fed rats. Treatment of Zn-deficient rats with salicylic acid produced a stronger although reversible hearing loss than in normally fed salicylate-treated rats. Treatment of Mg-deficient rats with gentamicin induced a strong hearing loss that was nearly complete and irreversible in 9 of 25 rats.
Abstract: Oral application of 700 mg/kg salicylic acid to pregnant and non-pregnant female rats caused an increase of serum Mg2+ and a decrease of serum Ca2+ concentration. The salicylate effect was drastically enhanced by Zn deficiency. The increase in serum Mg2+ is probably caused by the nephrotoxicity of salicylate. The decrease of serum Ca2+ concentration is combined with an increase of parathyroid hormone concentration in serum. Probably, salicylate and Zn deficiency inhibit Ca2+ mobilization by parathyroid hormone in bone.
Abstract: Nonhemoglobin Fe (non Hb-Fe) content in fetal serum and liver is much higher than in maternal serum and liver. After feeding a Zn-deficient diet to pregnant rats from d 0 to 21, non Hb-Fe content in maternal and fetal serum and liver was increased. After oral application of salicylic acid (300 mg/kg) from d 16 to 20 to normally fed and Zn-deficient dams, non Hb-Fe content in maternal and particularly in fetal serum and liver was drastically increased. In the kidney, Fe was accumulated to a small amount resulting from Zn deficiency and salicylate treatment. Fe accumulation in the liver occurred in all cell fractions, particularly in microsomes. Fe accumulation was confirmed and extended histochemically by Prussian blue staining. It is assumed that salicylate increases intestinal Fe resorption and fetal transfer of Fe. It is discussed that salicylate nephrotoxicity and its enhancement by Zn deficiency is not caused by an Fe-dependent mechanism.
Abstract: In the thymus of normally fed pregnant rats the plasma membrane enzymes dipeptidyl peptidase IV (DPP IV) and alkaline phosphatase (alP) were found in cortical and medullary lymphocytes (thymocytes). Plasma membrane aminopeptidase A (APA) and adenosine monophosphate hydrolysing phosphatase (AMPP) were present in cortical reticular cells. In medullary reticular cells, aminopeptidase M (APM), gamma-glutamyl transferase (GGT), adenosine triphosphate (ATPP) and thiamine pyrophosphate (TPPP) cleaving phosphatases were detected. Medullary reticular cells did not contain APA. Lysosomal DPP I and II, acid phosphatase, acid beta-D-galactosidase, beta-D-N-acetyl-glucosaminidase, beta-D-glucuronidase and non-specific esterases occurred especially in macrophages at the corticomedullary junction. The 21-day-old fetal thymus showed a similar reaction pattern as the maternal organ except for APA which was absent before birth. After treatment of the pregnant rats with valproic acid (VPA), salicylic acid (SA), streptozotocin (ST) and retinoic acid (RA) APA showed an increase in activity in the thymic cortex. In addition, ST and RA induced AMPP, ATPP and TPPP activity in cortical reticular cells up to the same pattern as in medullary reticular cells. After ethanol (ET) administration severe damages occurred. The thymic cortex was free of DPP IV-positive lymphocytes; the medullary reticular cells showed reduced or no GGT and occasionally an increased APM activity. Dexamethasone (DEXA) given to normal or zinc-deficient rats produced the most severe lesions; thymocytes with DPP IV activity were completely absent in the cortex and medulla. In Zn-deficient pregnant rats similar alterations were observed as after ET.(ABSTRACT TRUNCATED AT 250 WORDS)
Abstract: During net Mg2+ efflux from Mg2+-preloaded chicken erythrocytes, which occurs via Na+/Mg2+ antiport, 28Mg2+ is taken up intracellularly. Km of 28Mg2+ influx amounted to 1 mM. In Na+-free medium Vmax of 28Mg2+ influx was increased and Km was reduced to 0.2 mM. 28Mg2+ influx was noncompetitively inhibited by amiloride as was found for Na+/Mg2+ antiport. The results indicate that, extracellularly, Mg2+ can compete with Na+ for common binding sites of the Na+/Mg2+ antiporter, resulting in 28Mg2+-24Mg2+ exchange. The rate of Mg2+ exchange depends on extracellular Na+ and on the rate of net Mg2+ efflux.
Abstract: Coronary blood vessels of isolated spontaneously beating rat hearts were perfused with an Mg2+-free solution at a rate of 3 ml/min. 1.5-ml fractions were sampled. Net Mg2+ efflux from heart muscle cells was measured by the increase of Mg2+ concentration in the perfusate. Addition of 0.3 microM isoproterenol to the perfusate resulted in a rapidly occurring transient Mg2+ efflux which was inhibited by amiloride.
Abstract: Partially Mg2+-depleted Yoshida ascites tumor cells took up Mg2+ after reincubation in Mg2+- and HCO3(-)-containing media. Mg2+ influx was insensitive to ouabain, amiloride and disulfonic stilbenes, but was noncompetitively inhibited by furosemide (Ki = 0.4 mM) and bumetanide. Mg2+ influx obeyed Michaelis-Menten kinetics with respect to Mg2+ concentration (Km = 1.1 mM) and was sigmoidal with respect to HCO3- concentration. Electroneutral Mg2+, HCO3- cotransport was supposed to be the mechanism of Mg2+ influx.
Abstract: Mg2+ efflux from Mg2+-preloaded chicken erythrocytes is caused by an electroneutral Na+/Mg2+ antiport. It depends specifically on extracellular Na+, according to Michaelis-Menten kinetics (Km = 25 mM), and is reversibly noncompetitively inhibited by amiloride (Ki = 0.59 mM). In contrast to Na+/H+ antiport, Li+, Ca2+ and N-ethylmaleimide do not interfere with Na+/Mg2+ antiport. The Na+/Mg2+ antiport is driven by the intracellular/extracellular Mg2+ gradient.
Abstract: Desoxycorticosterone acetate (DOCA)-salt supersensitivity to isoprenaline (isoproterenol) was demonstrated by the increase in cardiac Na+ and Ca2+ content and by the decrease in cardiac Mg2+ content that occurs at lower isoprenaline doses in DOCA-salt pretreated rats compared to control rats. The number of beta-adrenoceptors in the myocardium as measured by [3H]-dihydroalprenolol binding amounted to 170 +/- 18 fmol/mg protein in normal rats and to 150 +/- 17 fmol/mg protein in DOCA-salt pretreated rats. The dissociation constant amounted to 2.6 +/- 0.4 nmol/l for normal and to 2.8 +/- 0.5 nmol/l for pretreated rats. The isoprenaline-induced increased cardiac Ca2+ content in DOCA-salt pretreated rats can be explained by the increased adenylate cyclase activity and by the resulting increased Ca2+ influx via phosphorylated calciductin.
Abstract: The lymphocytes of the rat thymus can be grossly differentiated by their cell membrane-bound proteinases. Subcapsular thymocytes lack aminopeptidase A (APA) and AMP and gamma-glutamyltranspeptidase (GGT). Cortical thymocytes show a high activity of APA but no APM and no GGT. Medullar thymocytes possess a high GGT and APM activity but are free of APA. Under Mg deficiency, the APA-negative subcapsular thymocytes are reduced. In lymphoma and beginning lymphoma, APA, APM and GGT are absent. In lymphoma, the alkaline phosphatase activity is increased. Differences are found for dipeptidylpeptidase IV (DPP IV). In some lymphoma, its activity is reduced, in others the DPP IV activity is increased.
Abstract: Pregnant rats were subcutaneously injected twice daily with 1.5 ml 150 mmol/l MgCl2 beginning at day 5 of gestation. By this treatment development of foetal liver and pancreas was enhanced. In the foetal liver, there was a precocious glycogenolysis combined with a precocious development of the smooth endoplasmic reticulum (ER) and an irregular arrangement of the rough ER. In the pancreas, the development of secretory granules was enhanced. In alizarin red-stained and cleared specimens, the foetal skeleton was less calcified. The injected Mg2+ remained extracellular. Altered hormonal secretion and/or an altered activity of the regulatory enzymes of glycogen metabolism induced by the increased extracellular Mg2+ concentration are discussed as possible mechanisms for enhanced foetal liver development.
Abstract: Chicken erythrocytes were loaded with Mg2+ by incubation with the cation ionophore A 23187 in the presence of Mg2+. After removing A 23187 by intensive washing with serum albumin and reincubating the Mg2+-loaded cells, Mg2+ was transported out of the cells until the original Mg2+ content was achieved. The net Mg2+ efflux followed Michaelis-Menten-kinetics and was independent of extracellular and intracellular Ca2+ and calmodulin. The net Mg2+ efflux was not affected by adrenalin, isoproterenol, p-chloromercuribenzenesulfonate, ouabain and tetrodotoxin, but was inhibited by dicyclohexylcarbodiimide, KCN, iodoacetate, high extracellular concentrations of Mg2+, Mn2+ and when extracellular Na+ was substituted by choline or K+. The efflux of 1 Mg2+ was coupled with the uptake of 2 Na+. It is concluded that there exists an additional gating process at the inner cell surface becoming active only at increased concentrations of intracellular free Mg2+ regulating the exit of Mg2+ by the efflux system.
Abstract: Malignant T cell lymphoma cells induced in the thymus by chronic Mg deficiency showed a less ruffled surface in the scanning electron microscope, particularly after intraperitoneal transplantation. Their content of phosphatidylserine and phosphatidylinositol was increased. The content of phosphatidylcholine, cholesterol and the cholesterol/phospholipid ratio, and thus membrane microviscosity, were decreased. The activity of phospholipid methyltransferase I and II was reduced. In parallel to these alterations, 45Ca2+ influx and efflux as well as 45Ca2+ content in mitochondria, microsomes and cytosol of lymphoma cells were enhanced.
Abstract: Female Sprague-Dawley rats kept on a standard chow or on a magnesium (Mg)-deficient diet during 6 days received s.c. injections of 0, 25, 50, 100 and 200 micrograms of epinephrine (Ep). 1 h before, they were orally treated with 0, 125 or 250 mg of Mg/kg b.w. given as magnesium aspartate hydrochloride. Drug-induced changes were studied by analyzing serum and cardiac tissue samples (Mg, Ca, K, Na and in addition glucose, FFA, cholesterol and creatine kinase in serum) taken at 7 different times (15 to 420 min) after treatment with Ep; effects were evaluated by considering the respective areas under the concentration-time curves (AUC). AUCs were calculated with linear and logarithmic graduation of the time-scale and were also transformed into logarithms. In additional experiments, animals of both diet groups were treated with Mg and Ep as described above and the hearts, excised after 420 min, were prepared for histological examination. Cardiotoxic effects induced by adrenergic overstimulation were aggravated by Mg deficiency. Most pronounced electrolyte alterations and histologically detectable cardiac necroses were observed in the Mg-deficient animals at 420 min following the s. c. injection of 200 micrograms of Ep. On the other hand, oral Mg treatment induced hypermagnesemia and reduced toxic effects of Ep--especially Ca overload of the heart muscle--in controls and in Mg-deficient rats.
Abstract: Pregnant rats were fed diets with an Mg2+ content of 40, 12, 6 and 3 mmol/kg from day 10-19 of pregnancy. There was a linear correlation of non-protein bound Mg2+ between foetal and maternal serum, between amniotic fluid and maternal serum, and between foetal serum and amniotic fluid, the ratios being 2.7, 2.0 and 1.3 respectively, indicating active transport of Mg2+ up to a constant concentration gradient by the placenta. In hearts, increases of Na+ and Ca2+, and decreases of Mg2+ and K+ were observed only in the group receiving the lowest Mg2+ supply. After i.v. injection of MgCl2 to pregnant rats, Mg2+ was slowly transported from maternal to foetal serum and more slowly into the amniotic fluid. The effect of isoproterenol on cardiac electrolyte content in pregnant rats was less than in non-pregnant rats, and the effect of isoproterenol in foetal rats was smaller than in maternal rats. These results are explained by inactivation of isoproterenol in the placenta, by the small diaplacental transport of isoproterenol and by a smaller isoproterenol-stimulation of foetal cardiac adenylate cyclase.
