The role of phosphate in the potentiation or amelioration of acute renal failure.

Alterations in the balance of several cations have been shown to affect the severity of acute renal failure. It has been suggested in both clinical and experimental studies that changes in phosphate balance can markedly potentiate as well as ameliorate the renal dysfunction seen in both acute and chronic nephropathies. To determine the role phosphate plays in the course of gentamicin-induced acute renal failure, we examined rats maintained on control, phosphate-supplemented, and phosphate-depleted diets. In both control and phosphate-supplemented groups of rats, the degree and severity of gentamicin-induced acute renal failure was similar. By contrast, renal function was better preserved in the phosphate-depleted group. Furthermore, morphologic evaluation revealed a significantly lower number of necrotic proximal tubule cells in phosphate-depleted rats when compared to the control or phosphate-replete rats. Renal cortical gentamicin concentrations were not different between the phosphate-depleted and phosphate-supplemented groups. We conclude that phosphate depletion is protective against nephrotoxicity. This effect appears to be independent of alterations in serum calcium, urinary calcium excretion and renal cortical gentamicin concentration.