Captopril fails to reverse hypertrophy of the left ventricle induced by aortic insufficiency in rabbits

Angiotensin converting enzyme (ACE) inhibition has been reported to induce regression of hypertrophy in several models of hemodynamic pressure overload. The aim of the present study was to determine whether the ACE inhibitor captopril can reduce hypertrophy of the left ventricle induced by a chronic volume overload and modify collagen composition of the hypertrophied myocardium. Rabbits with four months lasting aortic insufficiency were divided into two groups: treated with captopril (20 mg/kg/day) for five weeks and treated with placebo. The respective control groups were represented by sham-operated animals. Aortic insufficiency induced a decrease of diastolic pressure, an increase of systolic and pulse pressure, hypertrophy of the left and right ventricle, and an increase of hydroxyproline content in the left ventricle without a change of hydroxyproline concentrations in either ventricle. Captopril treatment further enhanced pulse pressure by decreasing diastolic blood pressure. Hypertrophy of the left ventricle, hydroxyproline content and concentration in both ventricles were unaffected by captopril treatment. It is concluded that ACE inhibition did not reverse the left ventricular hypertrophy developed as a result of overload induced by aortic insufficiency. We suggest that mechanisms different from activation of the renin-angiotensin system may play a decisive role in the maintenance of hypertrophy in this particular model of volume hemodynamic overload.