The effect of .ALPHA.1-blocker, bunazosin on a murine model of congestive heart failure induced by viral myocarditis.

The purpose of this study was to investigate the therapeutic effect of an alpha 1-blocker, bunazosin, using an experimental murine model of congestive heart failure induced by viral myocarditis. This model is characterized by a high incidence of severe myocarditis and subsequent congestive heart failure, and is suitable for the evaluation of the effect of drugs. To estimate myocardial damage objectively and quantitatively, we used antimyosin monoclonal antibody in addition to histopathological grading. Four-week-old BALB/c mice were inoculated with encephalomyocarditis virus. The mice were injected daily with bunazosin or saline as a placebo from the day of viral inoculation until day 7 (protocol-I) or day 14 (protocol-II), or from day 4 to day 14 (protocol-III). They were then injected with 1.5 microCi of indium-111 labeled antimyosin antibody and were killed 24 h later. The antimyosin cardiac uptake was counted and histopathological grading was performed. The heart-weight to body-weight ratio, left ventricular dimension, histopathological grades and antimyosin cardiac uptake were significantly lower in the bunazosin group than in the placebo group in protocol-II, but not in protocol-I or protocol-III. Bunazosin showed a protective effect against viral myocarditis only when it was started early after infection and continued until the stage of congestive heart failure.