Endothelium removal augments vasodilation by sodium nitroprusside and sodium nitrite

Sodium nitroprusside (3-100 nM) and sodium nitrite (0.03-1 mM) caused relaxation of the rat aortic ring segments precontracted by norepinephrine. The relaxation was significantly augmented by removal of endothelium, and this augmentation was greater in the aorta from spontaneously hypertensive rats (SHR) than Wistar Kyoto rats (WKY). The mechanism remains unknown but such augmentation may be clinically favorable to the use of nitrovasodilators.