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PubMed1994

Dietary chloride and urinary calcium in stone disease.

We studied six patients with renal stone disease, hypercalciuria, cystinuria and/or hyperuricosuria, during variations in dietary Na and Cl intake. Switching between equimolar NaCl and NaHCO3 intakes reduced urinary Ca (UCa) during the NaHCO3 phase, despite steady-state urinary Na. Switching between equimolar NaCl and KCl did not change UCa, despite a sharp fall in UNa. The results suggest a predominant role for Cl rather than Na ions during sodium-chloride-induced changes in UCa. In stone disease of mixed aetiology, where alkalinization of the urine as well as reduction in UCa may be desirable, treatment with NaHCO3 loading is not accompanied by a rise in UCa, provided that dietary Cl is maintained moderately low at 80-100 mmol/day. The mechanism whereby Cl intake influences UCa remains undefined. Plasma PTH and calcitriol levels showed no significant alteration, and atrial natriuretic peptide levels in one patient remained unchanged.

Calcium↗
PubMed1977

Factors controlling the nonprotein cystine content of cystinotic fibroblasts.

The cystine content of cystinotic fibroblasts increases with the length of time in cultivation. Four of five cystinotic cell strains showed an increase in cystine content with increased passage number. Cystinotic fibroblasts did not increase in cell number after 3 days in dialyzed fetal bovine serum. However, their cystine content increased almost 2-fold on a per cell number basis. Cystinotic cells incubated in cystine-free medium lost approximately 50% of their free cystine over a period of 12 hr and subsequently remained at about this level for 12 additional hr. Treatment of cystinotic cells with 1.0 mM dithiothreitol in complete medium reduced their free cystine content to about 25% of the initial level in 5 hr. The free cystine remained at this level after incubation overnight incystine-free medium without dithiothreitol. When dithiothreitol is added in the presence of a cystine-free medium, even more free cystine is removed from cystinotic cells (90%), and the free cystine content remains at this low level for as long as 48 hr if the cells are kept in a cystine-free medium. Cystinotic cells depleted of more than 50% of their intracellular free cystine by incubation in cystine-free medium reaccumulate cystine rapidly after replacement of cystine-containing medium. When cystinotic cells were depleted of their free cystine by treatment with dithiothreitol in a cystine-free medium and were then replaced in complete medium the intracellular free cystine reaccumulated rapidly, regaining its initial value in about 4 hr. The intracellular free cystine content found after 10 hr in complete medium reflected the cystine content of the medium. Cells in medium containing 0.266 mM cystine reaccumulated almost 60% more cystine than cells in medium with 0.066 mM cystine. When cystinotic and normal control fibroblasts were incubated for 2, 4, and 24 hr in either [35S]methionine or [35S]cystathionine, no radioactivity was recovered as cystine, cysteine, or glutathionine.

Cells, Cultured↗
PubMed1976

Cystine metabolism in human fibroblasts. Comparison of normal, cystinotic, and gamma-glutamylcysteine synethetase-deficient cells.

Incubation of normal human skin fibroblasts or fibroblasts derived from patients with erythrocyte deficiency of gamma-glutamylcysteine synthetase (gamma-glutamylcysteine synthetase-deficient) in culture medium containing L-[35S]cystine resulted in incorporation of radioactivity into protein, cysteine, and glutathione, gamma-Glutamylcysteine synthetase-deficient fibroblasts synthesized glutathione from [35S]cystine at 30% the rate of normal cells and contained 30% the normal amount of glutathione. Cystinotic fibroblasts incorporated [35S]cystine into the large intracellular cystine pool not found in normal or gamma-glutamylcysteine synthetase-deficient cells and also appeared to synthesize glutathione more slowly than normal cells. However, the radioactivity recovered as cystine was reduced greatly and the rate of [35S]cystine incorporation into glutathione increased if cystinotic cells were first depleted of their intracellular cystine pool before incubation in [35S]cystine. This suggests that the apparent reduced rate of glutathione synthesis observed in untreated cystinotic cells was a secondary effect caused by dilution of the [35S]cystine by the large pool of nonradioactive cystine. Cystinotic cells depleted of cystine by treatment with mercaptoethylamine reaccumulate 30 to 50% of their initial cystine in 24 hours in the absence of extracellular cystine. Both normal and cystinotic cells lose more than 90% of their intracellular glutathione in 24 hours in cystine-free medium. Both cell types can reutilize cysteine from glutathione for protein synthesis.

Amino Acid Metabolism, Inborn Errors↗