Decreased tubular reabsorption of zinc in rats with chronic uremia.

Effect of chronic uremia on tubular reabsorption of zinc was studied in rats with different zinc nutritional status. Using inulin clearance to represent glomerular filtration rate and plasma ultrafiltrate to imitate glomerular filtrate in vivo, the glomerular filtered load of zinc was estimated in each rat. The amount of tubular reabsorption of zinc equals the amount of zinc filtered minus the amount of zinc excreted into the urine. Proportion of filtered zinc excreted was estimated to be 2.8-8.7% in control rats and 17.3-29.8% in uremic rats induced by five-sixths nephrectomy. Similarly, proportion of filtered zinc reabsorption decreased significantly from 91.3-97.3% in control rats to 70.1-82.7% in uremic rats. Zinc deficiency increased fractional reabsorption of zinc in uremic rats but not in control rats. Fractional excretion of zinc correlated with both urine flow rate and urinary excretion of protein. The results suggest that uremia toxins may influence tubular reabsorption of zinc even in the presence of renal adaptation to zinc deficiency.