[Behavior of adenylate cyclase in ischemic and necrotic myocardial tissue]

The adenylate cyclase activity was determined in the left ventricles of rat hearts up to 60 min after severe ischemia and 24 hours after injection of a high dose of isoproterenol. The quantitative data show a progressive decline in the activity after 20 min of ischemia. Isoproterenol- and fluoride-stimulated activities were influenced in the same manner. The cytochemical localization showed no changes in the localization of the enzyme. But the number of cells with reaction products of the adenylate cyclase activity were decreased. The quantitative analysis of the adenylate cyclase activity in the myocardial necrosis produced by a single injection of 80 mg isoproterenol per kg body weight showed no changes in the basal activity of the enzyme however a significant reduction of the isoproterenol stimulation and a slight decrease of the fluoride-stimulated activity compared to the non-necrotic area of the same left ventricle. In cytochemical investigations no reaction of the adenylate cyclase activity was found in the centre of the necroses. But in the border zone of the basis the reaction product of the plasma membrane of the sarcolemma the main localization site of the enzyme activity was failed whereas the activity of the junctional SR was preserved. It was concluded that this activity is responsible for the unchanged basal activity in the necrotic and non-necrotic area.