Adenyl Cyclase and the Differentiation of β-Adrenoreceptors

WE have studied the enzyme adenyl cyclase to extend the evidence that β-adrenoreceptors consist of at least two types, β-1 and β-2 (refs. 1-4.) Cyclic 3′,5′-AMP has been shown to be the intracellular mediator of the action of various hormones, including the catecholamines, and it has been suggested that adenyl cyclase is an integral part of the β-adrenoreceptor5,6. Thus adenyl cyclase preparations from certain tissues should differ in their responsiveness to β-adrenoreceptor agonists and antagonists in a manner analogous to the intact tissues. We have therefore examined the differential effects of some sympathomimetic amines and their antagonists on the activity of adenyl cyclase preparations from rat heart and lung.