Effects of a new beta-adrenoceptor blocking agent, S-596 (arotinolol), on isolated dog coronary arteries

Effects of S-596 on dog coronary arteries were investigated in vitro. S-596 produced concentration-dependent relaxations of coronary arterial strips under potassium-, prostaglandin (PG) F2 alpha- or PGE2-contracture. S-596-induced relaxations of the strips were not influenced by tetraethylammonium or tranylcypromine, but restored by additional Ca++ or prevented by prior administration of Ca++. In distal portions of coronary arteries, S-596 significantly inhibited concentration-dependent relaxations of the strips induced by norepinephrine and reversed to weak contractions. In proximal portions, S-596 significantly inhibited concentration-dependent contractions induced by norepinephrine. Results indicate that S-596 has a nonspecific relaxant effect on isolated dog coronary arteries maybe through impairment of Ca++ availability and simultaneously has an alpha-adrenoceptor blocking effect, particularly on large coronary arteries.