Endothelium-dependent vasodilator effects of quercetin on hypertensive rat aorta.

Objective To determine effects of quecetin on vasorelaxation of hypertensive rat aorta.Methods Hypertensive rat model was made by Aortic-constriction method.Aortic ring from rats were suspended in organ baths containing Krebs solution,and then isometric tension was measured.The effects of quercetin on the aortic rings with or removal endothelium in hypertensive rats or normal blood pressure rats were determined,and Nω-nitrol-L-arginine methylester(L-NAME,nitric oxide synthase inhibitor),CHTX(potent and selective blocker of the calcium-activated potassium channel),indomethacin(cyclooxygenase inhibitor)were used to explore the mechanism.Results To both hypertensive rats and normal blood pressure rats,quercetin could produce relaxing of aortic rings preconstracted with noradrenaline in endothelium intact or denuded in a dose dependent manner.After endothelium in hypertensive Rat and normal blood pressure rat denuded,vasodilator effects of quercetin were significently decreased in every dose group(P0.05).Vasodilator effects of quercetin were more potent to hypertension model rats than control rats(P0.05).Pretreatment with L-NAME,the vasodilator effects of quercetin were significently decreased in hypentension group(P0.05).Pretreatment with CHTX or indomethacin,the vasorelaxation effects of quercetin were not significently decreased(P0.05).Conclusion Quercetin shows vasodilator effects of a dose-dependent manner and endothelium-dependent manner in hypertensive rats.The vasodilator effect of quercetin is mediated by endothelium nitric oxide pathway,but is unrelated to cyclooxygenase pathway or calcium-activated potassium channel pathway.