AJP - Cell Physiology, Vol 249, Issue 1 15-C19, Copyright © 1985 by American Physiological Society
Baboon erythrocyte ghosts contain beta-adrenergic receptors
E. E. Susanni, F. P. Ross, D. R. Scriven and C. Rosendorff
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.
