The effect of oral cilazapril and prazosin on the constrictor effects of locally infused angiotensin I and noradrenaline in human dorsal hand veins.

The effects of the ACE inhibitor cilazapril (5 mg p.o.) and the alpha 1-adrenoceptor blocker prazosin (2 mg p.o.) were investigated on the dose-response curves to angiotensin I and to noradrenaline, administered locally in the hand veins in six healthy male volunteers in doses not producing systemic effects. Both angiotensin I and noradrenaline produced a dose-dependent constriction of the congested veins. The angiotensin I effects were completely abolished after the administration of cilazapril but not significantly altered after the administration of prazosin. The noradrenaline dose-response curves were shifted to the right (dose ratio about 10) by prazosin, but not by cilazapril. The data suggest that angiotensin I, after having been converted to angiotensin II exerts direct venoconstrictor effects which under resting conditions are not mediated by noradrenaline release.