Effect of an ACE inhibitor and an AT1 receptor antagonist on cardiac hypertrophy

The effect of long-term administration of delapril, an angiotensin converting enzyme inhibitor, and candesartan, an angiotensin II receptor blocker, on cardiac hypertrophy was investigated in spontaneously hypertensive rats (SHR). Delapril (2 mg/kg/day) and candesartan (2 mg/kg/day) were administered for 5 weeks to 15-week-old male SHR. Echocardiographic estimation of cardiac morphology and function revealed cardiac hypertrophy in SHR compared with Wistar-Kyoto rats (WKY) which were used as normal controls. Both treated groups revealed regression of cardiac hypertrophy estimated by echocardiography. Heart to body weight ratio of treated SHR was also smaller than that of untreated SHR. Plasma BNP and ANP concentrations were increased in untreated SHR and decreased in the treated groups. Histological examination was performed using light microscopy and the area of fibrosis was estimated by computer. Reduction of the fibrotic area was observed in SHR treated with delapril and candesartan, although the latter was not statistically significant. Immunohistochemical examination using anti-collagen monoclonal antibody showed a decrease of type I collagen in treated SHR as compared with untreated SHR. It is concluded that both angiotensin converting enzyme inhibitor and angiotensin II receptor blocker sufficiently reduce blood pressure in SHR associated with regression of cardiac remodeling.