Vasodilator effects of bradykinin on the resistive circulation of the forearms of coronary patients

This study was undertaken to determine the vascular effects of bradykinin a nd its modes of action on the resistive circulation of the forearms of coro nary patients and healthy volunteers. Two groups were studied : Group I com prising 8 coronary patients with normal left ventricular function and Group II with 8 healthy volunteers. The method of measurement of forearm blood f low was occlusive venous plethysmography with a mercury strain gauge. The vasodilatory response of the two groups to local arterial perfusion of acetylcholine (40 and 80 mug/min), bradykinin (10. 30, 100 pmoles/min), the n the association of L-Ng-monomethyl-L-arginine (L-NMMA) at 8 muG/min, an i nhibitor of the synthesis of nitric oxide, with acety]choline and bradykini n. Five subjects of the control group received oral aspirin (250 mg/day) fo r one week before the study. Acetylcholine and bradykinin increased forearm flow in a dose-dependant manner but the increase was significantly less in coronary patients than in the healthy volunteers (p< 0.05). The L-NMMA inh ibited the vasodilatory response to acety]choline by about 40% in the two g roups but had no significant effect on the vasodilatation induced by bradyk inin. Aspirin had no effect on the vasodilatation induced by acetylcholine or bradykinin. These data show that the vasodilatory response to bradykinin is decreased i n coronary patients and suggest that nitric oxide is not the second main me ssenger of bradykinin in the resistive circulation of the forearm.