EARLY MYOCARDIAL LESIONS INDUCED BY CARDIOTOXIC COMPOUNDS IN SPRAGUE-DAWLEY RATS

Early focal myocardial lesions in rats induced by five cardiotoxic com pounds were histopathologically observed I hr and 4 hr after a single intravenous injection with 1/10 LD(50) and LD(50). The lesions were ob served I hr and 4 hr after the treatment with LD(50) of isoproterenol (ISP), 4 hr with 1/10 LD(50) of ISP, 4 hr with LD(50) of hydralazine ( HYD), caffeine (CAF) and cyclophosphamide (CYC), but not with adriamyc in (ADR). The lesions consisted of homogeneously intensely eosinophili c staining, contraction band formation and fragmentation of cardiac mu scle fibers. The lesions were interspersed in the inner one third of t he left ventricular walls including the papillary muscles with ISP, HY D and CAF, and were all over the ventricular myocardium with CYC.