Renal Vasodilatation Caused by Captopril in Conscious Normotensive and Goldblatt Hypertensive Dogs

Blood pressure and renal blood flow were monitored in conscious normotensive and two-kidney one-clip Goldblatt hypertensive dogs. Captopril administered IV in a single dose of 0.1 mg/kg to normotensives increased renal blood flow by 26.8 ± 7.6% and decreased renal vascular resistance, but did not significantly change blood pressure. Cumulative doses of 0.1 and 0.2 mg/kg increased renal blood flow by 29.9± 6.5%, and decreased renal vascular resistance and blood pressure significantly. Qualitatively similar changes in blood flow and vascular resistance of the contralateral kidney were obtained in the hypertensives. Blood pressure was reduced by a mean of 11.8 ± 4.5 mm Hg, renal blood flow increased by 36.2 ± 7.9% by the low dose, blood pressure decreased by 18.4 ± 2.7 mm Hg, and renal blood flow increased by 42.3 ± 11.4% by cumulative doses of the inhibitor. Plasma renin activity was increased by captopril in the normotensives and a greater increase in plasma renin activity was obtained in the hypertensives. The hypotensive and renal vasodilator effects of captopril appear to be related to blockade of the influence of the renin-angiotensin system, but another action, potentiation of kinin-induced vasodilatation, may also be involved.