BETA-ADRENERGIC-RECEPTOR LIGAND-BINDING BY RABBIT LUNG

The β-adrenergic receptor antagonists, [14C]propranolol and [3H]dihydroalprenolol, and [3H]dihydroergocryptine, an α-adrenergic receptor antagonist, were removed to the extent of 94, 84 and 78 per cent, respectively, from medium perfused through rabbit lung. Subcellular fractionation indicated that most (85-97 per cent) of the radiolabel was bound to particulate fractions of lung homogenates. Studies of [3H]dihydroalprenolol binding to membrane preparation, in vitro, revealed the presence of high affinity (KD = 0.5 nM) and high density (> 1 pmole/mg of protein) β-adrenergic-specific binding sites. Binding was stereospecific since (-)-propranolol was 250-fold more potent than (+)-propranolol in inhibiting the binding of [3H]dihydroalprenolol. © 1979.