Effects of verapamil on experimental cardiomyopathy in the Bio 14.6 Syrian hamster.

The Bio 14.6 Syrian hamster provides a good model for experimental study of cardiomyopathy. Cardiac receptor binding sites (alpha-1-, beta- and calcium antagonists) were studied in early (21 days old) and late (70 days old) stages of cardiomyopathy. The effects of verapamil on histologic features and free radicals in the heart were studied. The number of alpha-1- and beta-cardiac receptor binding sites was significantly greater in the late stage of cardiomyopathy when compared with findings in normal golden hamsters used as controls. The calcium antagonist receptors were significantly increased in the early stage but alpha-1- and beta-receptors were not. Verapamil-treated hamsters received intraperitoneal injections of verapamil at a dose of 5 mg/kg per day for 70 days from age 20 days. The percent areas of fibrosis and calcification in the verapamil-treated group were significantly smaller than those in the control group. The concentrations of lipid peroxides in the whole heart and free radicals in the heart mitochondria were significantly higher in the cardiomyopathic hamsters, and verapamil inhibited the increase in free radical concentration in the hearts of these hamsters. This study confirms that the number of calcium channels is increased early in the course of cardiomyopathy in the Bio 14.6 Syrian hamster. A larger number of free radicals may participate in the accumulation of calcium and cell injury in the myocytes of these hamsters. Verapamil protects against myocardial damage and may do so by inhibiting voltage-dependent calcium uptake and by preventing cell injury from free radicals.