MECHANISM OF RELAXANT EFFECTS OF NICORANDIL ON THE DOG CORONARY-ARTERY

  • 1 January 1983
    • journal article
    • research article
    • Vol. 265  (2) , 274-282
Abstract
To investigate the mechanism of the relaxant effects of nicorandil, a new coronary vasodilator, on the dog coronary artery, the effects of this substance on the K contracture were studied, and compared with those of nitroglycerin and nifedipine. All 3 substances induced a dose-related relaxation (nifedipine > nitroglycerin > nicorandil). The increase in La3+-resistant 45Ca uptake was inhibited only by nifedipine. In a Ca-free EGTA [ethylene glycol-bis-(.beta.-aminoethylether)-N,N''-tetraacetate] containing medium, caffeine induced a phasic contraction in the fully-depolarized preparation. Nicorandil produced an inhibition of this contraction, while nitroglycerin and nifedipine did not. Nicorandil evidently differs from the so-called Ca antagonists in the mechanism of relaxant action on the coronary artery. It also differs from nitroglycerin in that it produced an inhibition of caffeine-induced contraction.