Effects of nicorandil on the isolated smooth muscle preparation of the dog coronary artery

• Published in: Japanese journal of pharmacology Vol. 33; p. 257
• Main Authors: Tsukada, Tokumasa, Ushijima, Toyohiko, Nakazawa, Mikio, Imai, Shoichi
• Format: Journal Article
• Language: English
• Published: 1983
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)64843-2

Effects of nicorandil on the canine coronary artery were investigated with strips of the circumflex branch bathed in physiological salt solution (PSS) buffered with tris (hydroxymethy1) aminomethane (pH=7.4) aerated with oxygen and kept at 37°C. Nicorandil (10−5 −3×10−3 M) relaxed dose-relatedly the contracture induced by lanthanum in the calcium free, high K PSS(for the method, refer to Japan. J. Pharmacol. 31:221, 1981), as well as that produced by high K (127.7mM) PSS. Nitroglycerin relaxed both contractures also dose-relatedly. The ratio of potency of nicorandil and nitroglycerin was approximately one to thousand in both types of experiments. Caffeine (8-25mM) produced a contraction of this preparation in calcium free, high K PSS with 4mM of EGTA, which could be completely abolished by lOmM of procaine, suggesting that the contraction was due to a calcium-induced calcium release from its intracellular storage site. The contraction was reversibly suppressed to 68±7% of the control by nicorandil (1.4×10−3 M), while nitroglycerin was without effects, even with doses producing a complete inhibition of K-contracture, indicating that the mechanism for the arterial smooth muscle relaxant effect of nicorandil is different from that of nitroglycerin, although both compounds contain a nitrate group.