Biochemical mechanisms for regulation of β adrenergic receptors by β adrenergic agonists
Incubation of intact frog erythrocytes or purified frog erythrocytes plasma membranes with β-adrenergic agonists leads to a decreased number of functionally active β-adrenergic receptors which may be expressed as a desensitized or refractory state of adenylate cyclase to subsequent catecholamine stimulation. The data suggest that this desensitization process is mediated at least in part by alterations in the receptors themselves. Moreover, these alterations are likely to represent conformational alterations of the receptors induced by occupancy by agonists and to a lesser extent by partial agonists, but not by antagonists. The exact nature of these conformational alterations in the receptors is not yet clear. It must be remembered that receptor alterations are likely to represent only one of a number of potential mechanisms for the control of adenylate cyclase sensitivity to hormonal stimulation.
