Normal plasma total magnesium in Gitelman syndrome.
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Biomedical subjects
Publications and source records attributed to Anita C Truttmann.
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Regulation of magnesium balance is achieved by a steady-state mechanism in which intake and output are maintained at an equal level. Dietary magnesium intake, total and ionized plasma magnesium levels, and urinary magnesium were assessed in 46 renal transplant recipients treated with cyclosporine, nine transplant recipients who had never been on cyclosporine, and 31 healthy volunteers. Dietary magnesium intake [13.5 (11.0-15.1) mmol/day vs 13.0 (11.1-16.0) mmol/day and 13.7 (11.4-16.7) mmol/day, respectively; median and interquartile range] and urinary magnesium excretion [4.31 (3.57-5.89) vs 4.39 (3.56-6.02) and 5.01 (3.73-6.01) mmol/day, respectively] were similar in renal transplant recipients treated with cyclosporine, transplant recipients who had never been on cyclosporine, and control subjects. Total [0.74 (0.70-0.78) vs 0.80 (0.74-0.84) and 0.81 (0.79-0.87) mmol/l), respectively] and ionized [0.49 (0.46-0.52) vs 0.53 (0.50-0.58) and 0.54 (0.52-0.59) mmol/l, respectively] plasma magnesium were significantly lower in renal transplant recipients on cyclosporine than in transplant recipients without cyclosporine, and healthy controls. These observations indicate a modified magnesium steady state in renal transplant recipients treated with cyclosporine.
BACKGROUND: In view of the functional capacity of glutathione synthesis in premature infants, and because the availability of cysteine is one the rate limiting steps in glutathione synthesis, we hypothesized that the low glutathione levels in premature infants may be due to immaturity of the active cellular uptake of cysteine. OBJECTIVE: To document in cells from newborn infants the effect of maturity and gender on cysteine uptake and consequently on glutathione levels. METHODS: Incorporation of L-[35S] cysteine was measured in leukocytes from cord blood and from tracheal aspirates (TAC) of newborn infants of varying (gestational as well as postnatal) ages and gender. Cysteine uptake was correlated with glutathione in TAC. RESULTS: The maturity of newborn girls positively influences cysteine uptake, which is responsible for 78% of the variation in their glutathione content. However, in newborn boys, gestational and postnatal ages did not influence the cysteine uptake. DISCUSSION: Cysteine uptake appears to be the limiting step explaining the reported gender-related differences in glutathione as well as the low levels of this central antioxidant found in premature infants. The immature cysteine uptake found in cells from premature infants raises questions about the bioavailability of this conditionally essential amino acid in regimens of parenteral nutrition for human neonates.
BACKGROUND: Circulating magnesium exists in the bound and in the free ionized form, that is biologically active. In kidney disease the relationship between ionized and total circulating magnesium is often altered. Little information is available on the influence of hemodialysis on the relationship between ionized and total circulating magnesium in end-stage kidney disease. METHODS: Plasma total and ionized magnesium and the plasma ionized magnesium fraction were assessed before and after hemodialysis (dialysate magnesium content 0.75 mmol/l) in 46 patients with end-stage kidney disease and in a control group of 25 healthy subjects. RESULTS: In patients plasma total (from 1.19 [1.05-1.33] to 1.10 [1.02-1.16] mmol/l; median and interquartile range) and ionized (from 0.71 [0.66-0.78] to 0.65 [0.63-0.69] mmol/l) magnesium significantly decreased during dialysis (control subjects: 0.82 [0.80-0.92], respectively, 0.57 [0.54-0.59] mmol/l). The plasma ionized magnesium fraction was significantly lower in patients both before (0.61 [0.58-0.64)] and after (0.60 [0.56-0.62]) hemodialysis than in controls (0.68 [0.65-0.70]). CONCLUSIONS: The study demonstrates a tendency towards a reduced circulating ionized magnesium fraction in end-stage kidney disease that is not corrected by hemodialysis.