Prolonged inhibition of local angiotensin-converting enzyme after single or repeated treatment with quinapril in spontaneously hypertensive rats.

Plasma and tissue angiotensin-converting enzyme (ACE) activities were measured in spontaneously hypertensive rats (SHR) after single or repeated oral (p.o.) treatment with a hypotensive dose (1 mg/kg) of quinapril and compared with those after administration of enalapril (1 mg/kg). The degree of ACE inhibition in response to quinapril varied in tissues; marked inhibition was observed in aorta, lung, and plasma by single treatment with quinapril, and inhibition in plasma and aorta caused by quinapril was more potent than that caused by enalapril. The prolonged ACE inhibition was observed in the aorta, a target organ, by repeated treatment with quinapril for 2 weeks. These results indicate that quinapril has a good pharmacokinetic profile, namely rapid absorption and easy penetration to the target organ. In addition, quinapril produced greater inhibition of cardiac ACE than did enalapril after either p.o. or intravenous (i.v.) administration, suggesting the beneficial effects of quinapril in treatment of congestive heart failure (CHF).