Effects of metabolic acidosis on zinc and calcium metabolism in rats

To delineate the potential role of renal acidosis on zinc and calcium metabolism, 24 male Charles River rats, with a mean weight of 154 g, were assigned to four groups of 6 rats each. Three groups of rats were given ammonium chloride for 5 days by stomach tube at dosages of 4, 8, 16 mEq/kg/day, respectively. The control group received the solvent (normal saline) only. The animals were fed a semi-purified diet containing 100 ppm of zinc. The total food intake averaged 18, 16, 17 and 18g/day, respectively, for the control and the three treated groups. On the 4th and 5th day, two 24-hour urinary collections for net acid excretion, zinc and calcium excretions were obtained. The net acid excretion progressively increased from 0.85 ± 0.21 µEq/min/kg in the control rats to maximal values of 10.61 ± 0.87 µEq/min/kg in the acid-loaded rats. The net acid excretion is highly correlated with the urinary calcium excretion (r = 0.95, p < 0.01). However, the acid-loading has no effect on the carcass retention of zinc as documented by isotope studies or urinary zinc excretion.