Vasorelaxant effects of the bioflavonoid chrysin in isolated rat aorta

Chrysin relaxed the contractions induced by noradrenaline in isolated endot helium-intact rat aortic rings (IC50 = 16 +/- 4 muM). Endothelium removal a nd Nc-nitro-L-arginine methyl ester inhibited this relaxant effect. Chrysin potentiated the relaxation to acetylcholine under control conditions or af ter incubation with the superoxide anion generator hypoxanthine/xanthine ox idase. It also potentiated the relaxation induced by 3-morpholino-sydnonimi ne, sodium nitroprusside, and 8-bromoguanosine-3 ' :5 '- cyclic-monophospha te. Therefore, vasorelaxation induced by chrysin in the rat aorta is endoth elium- and NO-dependent. This effect is mediated by the prevention of O-2(- )-induced inactivation of endothelial derived NO and also by the potentiati on of cGMP-induced vasodilatation.