beta-Adrenergic receptors of frog erythrocytes. Biochemical sequelae following stimulation with isoproterenol.

Following persistent stimulation of beta-adrenergic receptors of frog erythrocytes with (-)-isoproterenol, the cyclic adenosine 3',5'-monophosphate-dependent protein kinase (cAMP-dependent protein kinase) (EC 2.7.1.37) was activated for several hours. This activation outlasted the duration of the increase of cAMP content. Following a persistant stimulation of beta-adrenergic receptors with isoproterenol, the phosphorylation of selective membrane proteins was increased. This increase in phosphorylation lasted longer than 4 hr but less than 12 hr. Between 2 and 4 hr after receptor stimulation the loss of beta-adrenergic receptor from plasma membrane was maximal, and the phosphorylation of two membrane proteins characterized by molecular weights of 60,000 and 38,000 daltons was selectively enhanced. In addition we found that isolated erythrocytes are capable of synthesizing RNA and polypeptides and that incubation with (-)-isoproterenol indices a long-term delayed increase of the synthesis of erythrocyte proteins. This increase in the synthesis of proteins appears to require new RNA synthesis. Thus the possibility can be entertained that this delayed increase in protein synthesis participates in the new synthesis of receptor and is operative in the termination of beta-adrenergic receptor subsensitivity elicited by a persistent stimulation with (-)-isoproterenol.