Abstract
Beta-adrenoceptor blocking activity of a newly synthesized benzothiazole derivative, 6-(2-hydroxy-3-isopropylamino) propoxybenzothiazole succinate (KF-577) was investigated. In in vitro preparation of the guinea pig trachea and the atrium it was approximately 1/100 and 1/10 as potent as propranolol, respectively, in competitively blocking the betareceptors : some cardioselectivity was seen. Like propranolol, it is devoid of intrinsic beta-stimulating activity. In urethane-anesthetized rats KF-577 and propranolol both exhibited a pressor effect at lower doses, while at higher doses both caused a sharp fall in blood pressure. The depressor and positive chronotropic effects of isoproterenol were both blocked by either KF-577 or propranolol. Mechanisms of this pressor effect were explored using vagotomized, adrenalectomized, reserpinized rats, and the results were subjected to discussion. KF-577 had a surface anesthetic potency 1/20 that of propranolol (guinea pig cornea) and a conduction anesthetic potency comparable to propranolol (frog sciatic nerve). KF-577 was thus shown to be a beta-adrenoceptor blocker having some selectivity.
