Superoxide Anions Contribute to Impaired Endothelium-Dependent Relaxation in Coronary Arteries of Young Cardiomyopathic Hamsters

A genetic model of cardiomyopathy, the Syrian cardiomyopathic hamster, is characterized by myocardial necrosis and dysfunction which may be initiated by inadequate coronary blood flow. The mechanisms mediating coronary vasospasm observed during the development of cardiomyopathy in this model are unknown. The present study utilized isolated coronary arteries (150-250 pm diameter) from cardiomyopathic (M) and Golden Syrian control (C) hamsters to determine if endothelial dysfunction was present during the necrotic stage of cardiomyopathy (60-90 days of age). Intraluminal diameter was continuously recorded in coronary arteries maintained at an intraluminal pressure of 40 mxnhg. In pre-constricted vessels, relaxation to the endothelium-dependent vasodilator, acetylcholine (ACh), was impaired in vessels from M compared to C hamsters. Inhibition of nitric oxide synthase activity with N-nitro-L-arginine (LNA) significantly reduced relaxation to ACh in coronary arteries from C hamsters. However, LNA had little ef...