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 × 10^–2M KCl, norephinephrine relaxed the strips in a concentration-dependent fashion. Propranolol (10^–6M) converted the norepinephrine-induced relaxations to contractions, and arotinolol (10^–6–10^–5M) 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^–6M) and inhibited by arotinolol (10^–6–10^–5M). These results suggest that arotinolol has an α-adrenoceptor blocking activity in addition to a β-adrenoceptor blocking action in dog coronary arteries.

Effects of Diltiazem on in Vitro Cardiovascular Actions of Crude Venom Obtained from Okinawan Box-Jellyfish (Habu-kurage), Chiropsalmus quadrigatus

“…Phentolamine, a non-selective α-adrenoceptor blocking agent 21 , at concentrations sufficient for α-adrenergic blockade in vitro 22 did not influence increases in developed tension of aortic preparations produced by the venom. This suggests that the calcium influx into vascular smooth muscle cells does not occur via receptor-operated calcium channels, and indirectly supports the hypothesis that the venom will induce calcium-influx into muscle cells via voltage-dependent calcium channels.…”