Zinc nutritional status modulates the 1,25-(OH)2D. Response in uremic rats

Previous studies from our laboratories have suggested that zinc depletion reduces the circulating level of 1,25-dihydroxycholecalciferol-1,25-(OH)2D-in phosphorus-depleted rats. Since calcitriol synthesis is in part dependent on renal function, we studied vitamin D metabolites, parathyroid hormone response, and mineral balance in animals with different zinc nutritional and renal functional status. Twenty-three male Lewis rats were pair fed with zinc-replete or zinc-deplete diets for 2 weeks. Thereafter, half of each paired group underwent nephrectomy, while half had sham operations. After a 4-week observation period, the zinc-depleted animals had lower plasma zinc levels, and nephrectomized animals had higher plasma creatinine concentrations than respective controls at sacrifice. Plasma calcium and phosphorus concentrations were similar in all four groups at sacrifice. The 25-hydroxycholecalciferol and parathyroid hormone concentrations were similar in groups with renal insufficiency, regardless of the zinc nutritional status. The mean plasma 1,25-(OH)2D concentration was 20 +/- 4 pg/ml in the zinc-replete/sham-control group. In the zinc-replete nephrectomized animals, the mean plasma 1,25-(OH)2D concentration was increased by 133% to 56 +/- 6 pg/ml, as compared with zinc-deplete nephrectomized group. There was a significant effect of renal function, zinc nutritional status, and the interaction of these factors in accounting for differences in mean 1,25-(OH)2D levels. Zinc-deplete groups had consistent negative net zinc balance. However, there was no consistent effect of zinc nutritional status on external calcium or phosphorus balance when nephrectomized groups of different zinc nutritional status were compared.(ABSTRACT TRUNCATED AT 250 WORDS)