Restoration of Norepinephrine Responsiveness of Solubilized Myocardial Adenylate Cyclase by Phosphatidylinositol

The addition of phosphatidylinositol totally restored the norepinephrine activation of the solubilized adenylate cyclase, whereas, phosphatodylserine and phosph atidylethanolamine did not.

Abstract

Abstract We have recently described the preparation of a solubilized cat myocardial adenylate cyclase which is unresponsive to norepinephrine, glucagon, histamine, and thyroxine, the hormones which activate the membrane-bound adenylate cyclase. The addition of phosphatidylinositol totally restored the norepinephrine activation of the solubilized adenylate cyclase, whereas, phosphatidylserine and phosphatidylethanolamine did not. Half-maximal activation was achieved with norepinephrine, 8 x 10-8 m, a concentration approximately 1% of that required in particulate preparations. Norepinephrine activation of adenylate cyclase in the presence of phosphatidylinositol was abolished by the beta adrenergic blocking agent, dl-propranolol.