Reduction of experimental gentamicin nephrotoxicity in rats by dietary calcium loading.

Since gentamicin accumulates in the renal cortex before renal failure and calcium reduces gentamicin binding to cell membranes, we examined the effect of dietary calcium loading on gentamicin toxicity in male F344 rats. Rats were fed either a normal (0.5%)- or a high (4%)-calcium-content chow. Calcium loading did not alter inulin clearance, urinary excretion of sodium or total osmoles, or serum ionized calcium. However, calcium loading caused elevation of urinary calcium excretion and lowered urinary cyclic AMP levels. The data suggest that calcium loading may have slowed the accumulation of gentamicin (40 mg/kg per day) by the renal cortex. Histological and functional evidence of nephrotoxicity was delayed in onset and attenuated in magnitude. The results indicate that dietary calcium loading reduces experimental gentamicin nephrotoxicity. Protection may be associated with slower renal cortical accumulation of gentamicin. Calcium-dependent membrane or intracellular events may mediate this effect.