Quinaprilat-induced vasodilatation in forearm vasculature of patients withessential hypertension: Comparison with enalaprilat

The aim of the present study was to assess the possible differences in hemo dynamic and neurohumoral responses to local ACE inhibition in the human for earm of patients with essential hypertension with either quinaprilat or ena laprilat. Forearm vascular responses to infusion of quinaprilat or enalapri lat (0.5 mug/dL/min) into the brachial artery were studied in 12 male patie nts with essential hypertension. The experiments were performed in a random ized, double-blind, crossover fashion. Before and during ACE inhibition, th e vasoconstrictor response to four cumulative doses of angiotensin I (Ang I ) was studied. Forearm blood flow was assessed using venous occlusion pleth ysmography. Local quinaprilat infusion induced a more rapid (even after 15 minutes; median vasodilation quinaprilat 29% vs. enalaprilat -1%, P < 0.02) and longer lasting forearm vasodilation as compared with enalaprilat. Afte r 15 minutes of local ACE inhibition, the vasoconstrictor response to Ang I was completely blocked by both ACE inhibitors. We conclude that in patient s with essential hypertension quinaprilat induces a more rapid and longer l asting vasodilatation than enalaprilat. These effects of quinaprilat are po ssibly related to its higher affinity for vascular ACE. On the other hand, the fact that these effects of quinaprilat were observed despite a similar degree of ACE inhibition as during enalaprilat may suggest that quinaprilat directly stimulates another vasodilatating mechanism.