Isolated Hormone Receptors

Abstract

DURING the past decade, the many and varied roles of the "second-messenger" cyclic AMP have become better understood.¹ Figure 1, based on the work of Sutherland et al.,² shows how hormones act on cyclic AMP. In this scheme, hormones that circulate in blood are the "first messengers." They interact with the enzyme adenyl cyclase in the plasma membranes of their target tissues, leading to the conversion of ATP to cyclic AMP, which then exerts the characteristic effects of the particular hormone. One of the intriguing features of this sequence is that it is, on the one hand, so general, and, on . . .