Baboon erythrocyte ghosts contain beta-adrenergic receptors.
We have used the beta-adrenergic antagonist [3H]dihydroalprenolol [( 3H]DHA) to identify binding sites on the erythrocyte membrane of the primate Papio ursinus. Analysis of the saturation isotherm revealed binding to be saturable with a maximal number of binding sites of 499 fmol/mg protein. [3H]DHA binds specifically to the erythrocyte ghosts with an apparent dissociation constant (Kd) of 0.57 +/- 0.06 nM. A similar value for Kd (0.46 +/- 0.07 nM) was evaluated from the rate constants of association (0.013 +/- 0.003 X nM-1 X min-1) and dissociation (0.006 +/- 0.001 X min-1). beta-adrenergic agonists compete for the binding sites with an order of potency (dl-isoproterenol greater than l-epinephrine greater than l-norepinephrine) typical of a beta 2-adrenergic receptor. Binding was shown to be stereospecific with l-stereoisomers being more potent than their corresponding d-stereoisomers in causing half-maximal inhibition. Isoproterenol stimulated the production of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) in a concentration-dependent manner, maximal levels (1.130 +/- 0.358 pmol cAMP/10(8) cells) being four times the basal levels. The results demonstrate the existence of a large number of beta-adrenergic receptors on baboon erythrocyte ghosts.
Susanni
E E
EE
Ross
F P
FP
Scriven
D R
DR
Rosendorff
C
C
D000818:Animals; D001667:Binding, Competitive; D000242:Cyclic AMP / Q000097:blood; D004082:Dihydroalprenolol / Q000097:blood; D004910:Erythrocyte Membrane / Q000378:metabolism*; D007700:Kinetics; D010215:Papio; D011943:Receptors, Adrenergic, beta / Q000032:analysis* / Q000145:classification
D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D000242:Cyclic AMP