The affinity of bopindolol and its two metabolites for a beta 2-adrenoceptor in the bovine mesenteric artery

Bopindolol and its two metabolites (18-502 and 20-785) were examined for their affinity to a beta 2-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 Kd and Bmax values of 0.86 +/- 0.16 nM, and 13.34 +/- 1.11 fmol/mg protein, respectively. The pKi values of bopindolol and its two metabolites for beta 2-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 beta 2-adrenoceptor tissue, and that bopindolol and its two metabolites were potent for beta 2-adrenoceptors in the bovine mesenteric artery.