Prevention of myocardial generation in hamsters with hereditary cardiomyopathy.

A number of drugs have been tested for their ability to prevent or change the course of skeletal and heart lesions occurring with a 100% incidence in cardiomyopathic hamsters (UM-X7.1). These drugs were selected because they act either on the metabolism or turnover of Ca or on adrenergic receptors. Verapamil (Isoptin), a potent inhibitor of myocardial transmembrane Ca conductivity, was found to completely prevent the myocardial lesions in myopathic hamsters. The hamsters were 28 to 30 days of age at the beginning of the experiment and were injected subcutaneously twice daily during 30 consecutive days in doses of 0.5 mg during the first week and 0.75 mg during the subsequent weeks. The protection afforded by Verapamil was no longer evident 30 days after interruption of the treatment. The severity of both cardiac and skeletal muscle lesions was found significantly lowered in hamsters receiving Dibenamine. It is assumed that Verapamil acts mainly by preventing excessive calcium influx in cardiomyocytes, whereas Dibenamine improves the microcirculation, which is deficient during the necrotizing phase of the polymyopathy. The latter assumption rests on the fact that, in myopathic hamsters, the reactivity pattern of alkaline phosphatase is altered at the level of the capillaries of cardiac and skeletal muscles.