Effects of intrarenal infusion of calcium entry blockers in anesthetized dogs.

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Abstract
Renal function and renin release were studied in anesthetized, uninephrectomized dogs during intrarenal infusions of the calcium influx blockers, verapamil and nifedipine. Verapamil increased renal blood flow by 20% (p less than 0.05) but did not alter glomerular filtration rate. Verapamil produced five-to-seven fold increases in urine flow and the rates of excretion of sodium and chloride (p less than 0.01). Significant increases in the rates of excretion of potassium, calcium and magnesium were also observed. Despite its striking effects on renal function, verapamil, in nonhypotensive doses, failed to alter renin secretion. Intrarenal infusion of nifedipine had no consistent effect on renal blood flow or the rate of glomerular filtration but increased urine flow and the rates of excretion of sodium and chloride by more than three fold (p less than 0.01). Nonhypotensive doses of nifedipine had no significant effect on renin release. In dogs with a denervated nonfiltering kidney, an intrarenal verapamil or nifedipine infusion did not produce a significant change in renin release. This study demonstrates a striking effect of calcium entry blockers on the reabsorption of sodium, chloride, and water by the renal tubules in intact dogs but renin release did not increase unless hypotension occurred.