Possible α-Adrenoceptor Blocking Activity of Arotinolol (S-596), a New β-Adrenoceptor Blocking Agent in Isolated Dog Coronary Artery

Abstract

Effects of arotinolol on dog coronary arteries were investigated in vitro. In distal portions of left circumflex coronary arteries contracted with 3 X 10(-2)M KCl, norephinephrine relaxed the strips in a concentration-dependent fashion. Propranolol (10(-6)M) converted the norepinephrine-induced relaxations to contractions, and arotinolol (10(-6)-10(-5)M) inhibited the relaxations induced by norepinephrine in a concentration-dependent manner. In proximal portions of the strips after potassium-contracture, norephinephrine produced concentration-dependent contractions which were augmented by propranolol (10(-6)M) and inhibited by arotinolol (10(-6)-10(-5)M). These results suggest that arotinolol has an alpha-adrenoceptor blocking activity in addition to a beta-adrenoceptor blocking action in dog coronary arteries.