Cardiomyopathic hamster hearts: long-term effects of drugs on catecholamine contents and binding characteristics of alpha 1- and beta 1-adrenergic receptors.

Changes were examined in myocardial catecholamine content and alpha 1- and beta 1-adrenoceptors during the development of cardiomyopathy in Syrian hamsters (Bio 14.6) and age-matched healthy controls. In addition, the effects of bunazosin, atenolol, xamoterol, ketanserin, and verapamil on the catecholamine content and [3H]prazosin, [3H]CGP12177 bindings to alpha 1- and beta 1-adrenergic receptors of myocardium were compared with those of the controls. (1) Lower norepinephrine and dopamine levels were observed in 35-week-old cardiomyopathic hamster hearts than in the controls. There was, however, a tendency for a slight decrease of alpha 1- and beta 1-adrenoceptors in cardiomyopathic hamsters. (2) Administration of bunazosin induced lower dopamine values in 18-week-old cardiomyopathic hamsters. (3) Xamoterol induced a higher Kd value for beta 1-adrenoceptors and lower dopamine content than for those with cardiomyopathy. Ketanserin also induced a higher Bmax value than for cardiomyopathy. Thus, drug treatments clearly change catecholamine content and binding characteristics of the adrenoceptors which play an important role in the development of cardiac hypertrophy and heart failure.