Histochemistry of ventricular heavy-chain myosins in cardiomyopathic Syrian hamsters treated with D-600.

Monoclonal antibodies (MAb) have been used to study the distribution of ventricular heavy-chain (HC) myosins in cardiomyopathic UM-X7.1 Syrian hamsters. The Ab were identified as alpha and beta anti-HC myosins because of their ability to cross-react with ventricular V1 and V3 myosins, respectively. Cryostat frozen sections from the midventricle region of normal and myopathic hearts were processed for demonstration of these isomyosins by indirect immunofluorescence. In myopathic hearts, there was a shift of predominant alpha myosin toward the beta isoform with the time course of the hamster cardiomyopathy. A D-600 treatment while preventing cardiac necrotic lesions had little or no effect on the beta isomyosin conversion. It is inferred that the isomyosin shift during the progression of the hamster cardiomyopathy is unrelated to the necrotizing process and merely reflects the hypokynetism of the cardiomyocytes.