The binding characteristics and number of β adrenergic receptors on the turkey erythrocyte

Turkey erythrocyte ghosts (empty membranes) possess a class of receptors that can bind both L (3H)isoproterenol and DL (3H)propranolol. The binding of (³H)isoproterenol to these receptors occurs with a dissociation constant of 0.15 μM and can be fully inhibited by 1 μM propranolol. The binding of (³H)propranolol occurs with a dissociation constant of 2.5 nM and can be fully inhibited by 0.2 mM DL isoproterenol. Ligand binding is sensitive to sonication, boiling, and 8 M urea. The cells possess 500 to 1000 β adrenergic receptors per cell. Binding of propranolol to the β receptor was found to be stereospecific for the L stereoisomer. If one assumed a 1:1 relationship between β adrenergic receptors and adenylate cyclase, the turnover number of this adenylate cyclase would be close to 100/min. (13 references)