The Affinity of Bopindolol and Its Two Metabolites for a β₂-Adrenoceptor in the Bovine Mesenteric Artery

Abstract

Bopindolol and its two metabolites (18-502 and 20-785) were examined for their affinity to a β₂-adrenoceptor in the bovine mesenteric artery using the radioligand binding assay method with [³H]CGP12177 as a radioligand. The Scatchard analysis of the data demonstrated a uniphasic plot with K_d and B_max values of 0.86±0.16 nM, and 13.34±1.11 fmol/mg protein, respectively. The pK_i values of bopindolol and its two metabolites for β₂-adrenoceptors in the bovine mesenteric artery were 7.70±0.13, 8.07±0.13, 8.20±0.24, respectively, with 20-785 showing the highest values among these drugs. The present findings indicate that the bovine mesenteric artery membrane is predominantly β₂-adrenoceptor tissue, and that bopindolol and its two metabolites were potent for β₂-adrenoceptors in the bovine mesenteric artery.