Vasodilative effect of nicorandil on coronary artery

Vasodilative effects of nicorandil (2-nicotinamidoethylnitrate) and verapamil were compared using isolated canine coronary arterial strips contracted with either high potassium or prostaglandin F2 alpha (PGF2 alpha). When the vasodilative effects of these drugs were determined at 15 min after the application, nicorandil induced a dose-dependent relaxation of the strips contracted with high K. Vasodilative effect of nicorandil was inversely proportional to the concentration of K used to contract the arteries, showing 82 +/- 3.0% (mean +/- SE) and 21 +/- 3.6 of relaxation at the highest concentration of this drug (10(-5) mol/l) when the strips were contracted with 20 and 100 mmol/l K, respectively. Vasodilative effect of nicorandil on PGF2 alpha-induced contraction was found to be almost the same as that on 30 K-induced contraction. In contrast to nicorandil, verapamil induced a potent vasodilation of the coronary strips contracted with high K by a dose-dependent manner. Verapamil at the concentration of 10(-5) mol/l was found to induce a potent relaxation (87 +/- 0.8%) of the strips contracted with 100 K. However, verapamil showed a weak vasodilative effect on the strips contracted with PGF2 alpha (10(-5) mol/l), i.e., 10(-5) mol/l verapamil induced 22 +/- 1.1% relaxation of PGF2 alpha-induced coronary strips. These results suggest that nicorandil can exert its vasodilative effect against the coronary arterial contraction induced not only by high K, which is induced by a voltage dependent Ca influx, but also by PGF2 alpha, which is considered to be through the specific receptor of the membranes.(ABSTRACT TRUNCATED AT 250 WORDS)