EFFECT OF LOSARTAN ON RIGHT-VENTRICULAR HYPERTROPHY AND CARDIAC ANGIOTENSIN I-CONVERTING ENZYME-ACTIVITY IN PULMONARY HYPERTENSIVE RATS

The aim of this study was to investigate the effect of prophylactic tr eatment with the angiotensin type 1 (AT(1)) receptor antagonist losart an on right ventricular hypertrophy and cardiac angiotensin I-converti ng enzyme (ACE) activity in a rat model of monocrotaline-induced pulmo nary hypertension. Losartan failed to prevent either pulmonary hyperte nsion or right ventricular hypertrophy. Right ventricular ACE in untre ated pulmonary hypertensive rats did not differ from control rats. Los artan treatment in pulmonary hypertensive rats caused a significant 2- fold increase of ACE activity in the hypertrophied right (p<0.005) but not in the left ventricle. Thus, cardiac ACE activity is not stimulat ed in rats with monocrotaline-induced right ventricular hypertrophy. P rophylactic losartan treatment in this model of progressive pulmonary hypertension failed to prevent or reduce the increase in ventricular a fterload. The relevance of the increase in right ventricular ACE activ ity during pulmonary hypertension after losartan treatment is unknown and needs to be evaluated in further studies.