Endothelium is involved in the vasorelaxation by an ATP-sensitive K+ channel opener, NIP-121

Possible involvement of endothelium was examined in the vasorelaxation of rat aorta in response to NIP-121 ((+)-7,8-dihydro-6,6-dimethyl-7-hyroxy-8-(2-oxo-1-piperidinyl)-6H- pyrano[2,3-f]benz-2,1,3-oxadiazole), an ATP-sensitive K+ (K(ATP)) channel opener. The NIP-121-induced vasorelaxation was greater in endothelium-intact preparations than in endothelium-denuded ones. In the presence of glibenclamide, which inhibits K(ATP) channels, NIP-121-induced vasorelaxations were of a similar extent in both endothelium-intact and -denuded preparations. These findings suggest that the presence of endothelium plays a role in the vasorelaxation in response to K(ATP) channel openers.