Systemic and regional hemodynamic profile of five angiotensin I converting enzyme inhibitors in the spontaneously hypertensive rat.

The effects of 5 angiotensin I converting enzyme (ACE) inhibitors--captopril, enalapril, perindopril, trandolapril and ramipril--on general and regional hemodynamics were investigated (using radioactive microspheres) and compared in anesthetized adult spontaneously hypertensive rats. The 5 treatments were administered daily by gavage for 8 days in doses inducing identical decreases in arterial blood pressure. This effect was entirely due to a decrease in total peripheral resistance inasmuch as cardiac index was not affected by the 5 ACE inhibitors. In addition, despite their different chemical structures, all exhibited the same regional vasodilator pattern, which thus appears to be related only to ACE inhibition. The vascular beds resistances were decreased in the following order: renal greater than splenic = liver greater than skin greater than total peripheral greater than muscle = brain. Simultaneously, and despite the decrease in perfusion pressure, most regional blood flows and especially renal blood flow were increased. Finally, renal vasodilator effects of ACE inhibitors were observed even after doses that lacked any effect on total peripheral resistance.