Different steric characteristics of beta 1- and beta 2-adrenoceptors

beta-Adrenoceptors of lung (75% beta 2) and heart (95% beta 1) of calf were labelled with 3H-(-)-propranolol. The stereoisomers of 10 ligands were used to inhibit the binding of 3H-(-)-propranolol to membrane particles. The affinity ratio of stereoisomers is consistently greater for beta 1-adrenoceptors than for beta 2-adrenoceptors, regardless of whether the ligands are agonists, partial agonists or antagonists. The beta 1-adrenoceptor appears to possess stricter steric requirements than the beta 2-adrenoceptor. This property may prove helpful in differentiating the beta-adrenoceptor subtypes during receptor solubilization and purification.