Renal Vasodilator Responses to Captopril in Dogs Pretreated with Indomethacin

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Abstract
Renal vasodilator responses to captopril administered i.v. were evaluated in pentobarbital anesthetized dogs pretreated with indomethacin to determine whether synthesis and release of vasodilator prostaglandins are involved in the response. Renal artery blood flow was measured using electromagnetic flowmetry and renal vascular resistance was calculated from the ratio of mean arterial blood pressure/renal artery blood flow. In control dogs captopril caused significant dose-related increases (ranging from 9 .+-. 2 to 37 .+-. 6 ml/min) in renal artery blood flow and decreases in renal vascular resistance. The drug decreased mean arterial blood pressure by 22 .+-. 3 mmHg; heart rate was not significantly altered from precaptopril control values. In indomethacin pretreated dogs, the renal vasodilator and systemic hypotensive responses of captopril were not attenuated. Captopril apparently causes renal vasodilation by a mechanism independent of prostaglandins.