Influence of ramipril diacid on the peripheral vascular effects of angiotensin I

Studies were performed to examine the effect on forearm blood flow of local brachial artery infusions of angiotensin I, angiotensin II and of the converting enzyme inhibitor ramipril diacid (the active metabolite of ramipril). Acute infusions of both angiotensins produced dose-dependent decreases in blood flow (measured by venous occlusion plethysmography). To produce equivalent effects the dose of angiotensin I was 2 to 4 times that of angiotensin II. After ramipril diacid the response to angiotensin II was unchanged, while the dose of angiotensin I required to produce an equipotent response was increased 20-fold. Ramipril diacid given alone produced a small, nonsignificant increase in forearm flow, although the response was significantly related to basal plasma renin. The study confirms the presence of converting enzyme activity within human resistance vessels, and suggests that inhibition of converting enzyme, at sites other than the pulmonary vascular bed, might contribute to the hypotensive action of converting enzyme inhibitors.