DIFFERENT EFFECTS OF AN ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR AND ACALCIUM-ANTAGONIST ON PROTEIN-METABOLISM IN RATS WITH RIGHT-VENTRICULAR HYPERTROPHY

Objective: We examined the effects of a calcium antagonist and an angi otensin converting enzyme (ACE) inhibitor on contractile and non-contr actile protein metabolism and cardiac function in a monocrotaline-indu ced right ventricular hypertrophy model, in order to define the effect s of these drugs on cardiac hypertrophy. Methods: One week after monoc rotaline injection, male Sprague-Dawley rats were given either a calci um antagonist (nilvadipine; 3 mg/kg per day) or an ACE inhibitor (dela pril-HCl; 30 mg/kg per day) for 2 weeks. Right ventricular pressure, t he right ventricle:(left ventricle + interventricular septum) ratio, m yosin isoenzymes, collagen concentration, collagen types and contracti lity of right ventricular free wall were examined. Results: In untreat ed rats significant monocrotaline-induced right ventricular hypertroph y with an increase in the proportion of collagen types III and V was o bserved. There were no significant changes in collagen concentration. Both drugs reduced right ventricular pressure to the same degree and d ecreased right ventricular hypertrophy. However, the inhibitory effect of delapril on right ventricular hypertrophy was stronger than that o f nilvadipine. Nilvadipine reduced the collagen concentration and reve rsed changes in collagen types, whereas delapril did not have any sign ificant effect on collagen concentration or collagen types. Cardiac co ntractility was improved by delapril, but not by nilvadipine. Conclusi ons: The results show that a calcium antagonist disproportionately inh ibited contractile and non-contractile protein metabolism, whereas an ACE inhibitor proportionally inhibited them and improved cardiac funct ion in a model of right ventricular hypertrophy. The improvement in ca rdiac function may be due partly to the proportional inhibition of con tractile and non-contractile proteins elicited by an ACE inhibitor.