Vasorelaxant effects of the bioflavonoid chrysin in isolated rat aorta.

Chrysin relaxed the contractions induced by noradrenaline in isolated endothelium-intact rat aortic rings (IC(50) = 16 +/- 4 microM). Endothelium removal and N(G)-nitro-L-arginine methyl ester inhibited this relaxant effect. Chrysin potentiated the relaxation to acetylcholine under control conditions or after incubation with the superoxide anion generator hypoxanthine/xanthine oxidase. It also potentiated the relaxation induced by 3-morpholino-sydnonimine, sodium nitroprusside, and 8-bromoguanosine-3':5'-cyclic-monophosphate. Therefore, vasorelaxation induced by chrysin in the rat aorta is endothelium- and NO-dependent. This effect is mediated by the prevention of O(2)(-)-induced inactivation of endothelial derived NO and also by the potentiation of cGMP-induced vasodilatation.