The development of regenerative and plastic myocardial insufficiency induced by anthracycline antibiotic rubomycin is accompanied by a decrease in cardiomyocyte sensitivity to damage produced by synthetic catecholamine isoproterenol. The incidence and the size of coagulation necrosis foci of cardiomyocytes developed 6 h after isoproterenol injection significantly decreased with increasing in the interval between rubomycin injection and subsequent administration of isoproterenol. In Wistar rats receiving rubomycin 3-5 days prior to isoproterenol and exhibiting signs of regenerative and plastic insufficiency, no cardiomyocyte contracture, intracellular myocytolysis, or lump degradation characteristic of cardiac insufficiency induced by endo- and exogenous catecholamines were found.