l-arginine-induced dilatation of goat coronary artery involves activation of KATP channels

In the present study, the mechanism of relaxant response of nitric oxide precursor, l-arginine, was investigated in goat isolated coronary artery. l-arginine (1 mM) reversed the U-46619 (1 µM)-induced contraction both in endothelium-intact and endothelium-denuded arterial ring preparations. l-arginine analogues, l-NAME, l-NNA and l-NMMA and the guanylyl cyclase inhibitor, methylene blue failed to attenuate the relaxant response of l-arginine. These observations negate the involvement of nitric oxide in mediating the relaxation by l-arginine. KATP channel blocker, glibenclamide (3 µM), abolished the vasorelaxant responses of l-arginine in endothelium-denuded preparations, thereby suggesting the involvement of KATP channels. Further, l-arginine also failed to induce relaxation of the coronary arterial rings constricted with K+ (80 mM)-PSS. Taken together, the results of the present study suggest that l- arginine relaxes goat isolated coronary artery through activation of KATP channels.