Comparison of cardiac lesions induced in rats by isoproterenol and by repeated stress of restraint and water immersion with special reference to etiology of cardiomyopathy.

Cardiac lesions induced in rats by isoproterenol, a potent beta-agonist, and by repeated stress of restraint and water immersion, in which sensitization of beta-adrenergic receptors would be expected to be induced, were investigated morphologically and following facts were revealed. 1) Cardiac lesions induced by isoproterenol, characteristic findings of which were myocardial hypertrophy, myocardial degeneration and myocardial necrosis replaced by interstitial fibrosis, were more analogous to cardiomyopathy than myocardial infarction or cardiac hypertrophy. 2) Cardiac lesions induced by repeated stress of restraint and water immersion, characteristic findings of which were myocardial hypertrophy, myocardial degeneration and myocardial necrosis replaced by interstitial fibrosis, were similar to those induced by isoproterenol. These results suggest that the endogenously induced dominant beta-adrenergic stimulating action during stress may play an important role in the pathogenesis of cardiomyopathy, the specific etiology of which is not yet known.