Vasodilation effect of quercetin on rat thoracic aorta and its mechanisms

AIM To investigate the vasodilation effect and the related mechanisms of quercetin. METHODS Tension was measured to evaluate the vasodilation effect of quercetin on rat endothelium-intact and endothelium-denuded thoracic aorta rings.The nitric oxide synthase inhibitor N~ω-nitro-L-arginine methyl ester (L-NAME),guanylyl cyclase inhibitor methylene blue,cyclooxygenase inhibitor indomethacin,calciumactivated potassium channel blocker tetraethyl ammonium(TEA),ATP-sensitive potassium channel blocker glibencla- mide and voltage-dependent potassium channel blocker 4-aminopyridine(4-AP) were used to illustrate the mechanisms of vasodilation effect of quercetin.RESULTS Quercetin(1,3,10,30,100,300μmol·L~(-1)) relaxed aortic rings pre-contracted with norepinephrine(NE,1μmol·L~(-1)) or KCl(80 mmol-L1).Pretreatment with quercetin noncompetitively inhibited contractile responses of aortas to NE or KCl.The vasorelaxant effect of quercetin did not rely on intact endothelia(P0.05).Pretreatment with L-NAME(100μmol·L~(-1)) significantly reduced the quercetin-induced vasodilation(P0.05).However,methylene blue(10μmol·L~(-1)) and indomethacin (5μmol·L~(-1)) showed no significant inhibit effects(P0.05).In endothelium-denuded rings,TEA (5 mmol·L~(-1)) significantly attenuated the vasorelaxant effect of quercetin,while glibenclamide(10μol·L~(-1)) and 4-AP(100μmol·L~(-1)) had no impact on it(P0.05).CONCLUSION The results suggested that quercetin induced relaxation in rat aortic rings through an endothelium-independent manner by blockade of Ca~(2+) channels.The opening of calcium-activated K~+ channels in vascular smooth muscle cells might also be one of the mechanisms.