Assessment of Partial Agonist Activity of Bopindolol and Its Two Metabolites (18–502 and 20–785) to β2‐Adrenoceptors in Tracheal Smooth Muscles of Guinea‐pigs

The partial agonist activity of bopindolol and its two metabolites (18–502 (4-(3-tert-butylamino-2-hydroxypropoxy)-2-methyl indole) and 20–785 (4-(3-tert-butylaminopropoxy)-2-carboxyl indole)) to β2 adrenoceptors in tracheal smooth muscles of guinea-pigs were determined. The oxidized metabolite, 20–785, showed high partial agonist activity, although this activity was weaker than that of pindolol. On the other hand, bopindolol and the hydrolysis product, 18–502, had low partial agonist activity. Thus, this study showed that the partial agonist activity to β2 adrenoceptors in the tracheal smooth muscles may be dependent on this one metabolite.