OBJECTIVETo investigate the different effects of an angiotensin II type 1 (AT(1)) receptor antagonist, losartan, and an angiotensin converting enzyme (ACE) inhibitor, fosinopril, on cardiomyocyte apoptosis, myocardial fibrosis, and angiotensin II (Ang II) in the left ventricle of spontaneously hypertensive rats (SHRs).

METHODSSHRs of 16-week-old were randomly divided into 3 groups: SHR-L (treated with losartan, 30 mg.kg(-1) x d(-1)), SHR-F (treated with fosinopril, 10 mg x kg(-1) x d(-1)), and SHR-C (treated with placebo). Each group consisted of 10 rats. Five rats, randomly selected from each group, were killed at the 8th and 16th week after treatment. Cardiomyocyte apoptosis, collagen volume fraction (CVF), perivascular collagen area (PVCA) and Ang II concentrations of plasma and myocardium were examined.

RESULTSCompared with the controls at the 8th and 16th week, systolic blood pressures were similarly decreased in both treatment groups. Left ventricular weight and left ventricular mass indexes were significantly lower in both treatment groups. However, the latter parameter at the 16th week was reduced to a less extent in the fosinopril group than that in the losartan group. Compared with the controls, cardiomycyte apoptotic index was significantly reduced at the 8th week only in the fosinopril group, and at the 16th week in both treatment groups. The index of the fosinopril group was lower than that of the losartan group at the latter endpoint examined. Compared with the controls, the left ventricular collagen volume fraction and perivascular collagen area at the 8th and 16th weeks were significantly reduced in the SHRs treated with either fosinopril or losartan. However, the collagen volume fraction at the latter endpoint in the fosinopril group was lower than that in the losartan group. Compared with the controls at endpoints, plasma and myocardium Ang II levels were significantly increased in the losartan group. However, plasma Ang II concentrations were not altered, and myocardium Ang II concentrations at the 8th and 16th weeks were significantly reduced in the fosinopril group.

CONCLUSIONSBoth losartan and fosinopril could effectively inhibit cardiomyocyte apoptosis and myocardial fibrosis and reverse heart hypertrophy. Fosinopril may be more effective in these cardioprotective effects, suggesting that the effects of both drugs are related to the inhibition of myocardium renin-angiotension-aldsterone system.