Adenylate cyclase activities of the sarcotubular membranes of the genetically myopathic hamsters

Abstract

The adenylate cyclase activities of the cardiac and skeletal muscle sarcotubular membranes of the genetically myopathic hamsters (BIO 14.6) at moderate and late stages of myopathy were determined. The basal adenylate cyclase activities of the sarcotubular membranes of the myopathic heart and skeletal muscle were not different from the control values. Unlike skeletal muscle, the cardiac sarcotubular adenylate cyclase of the myopathic hamsters at moderate stages was not activated by catecholamines. The activation due to NaF of the enzyme was significantly depressed, whereas catecholamines failed to activate the enzyme in both cardiac and skeletal muscle preparations from animals at late stages of myopathy. The observed alterations in the responsiveness of the adenylate cyclase to its activators at late stages of myopathy may be due to structural damage to the sarcotubular systems of the cardiac and skeletal muscles of the myopathic hamsters.