Objectives : The purpose of this study is to investigate vasorelaxation effect of Epimedium koreanum(EK) extract on rabbit carotid artery.

Methods : In this study, to determine vasorelaxation effect of EK extract on rabbit carotid artery, arterial rings with intact or damaged endothelium were used for experiment using organ bath, and were contracted by norepinephrine(NE). After contracting, arterial rings were treated with EK extract in a dose-dependent manner.
To study its mechanism, the contracted arterial rings induced by NE were pretreated with indomethacin(IM), Nω-nitro-L-arginine(L-NNA), methylene blue(MB) or tetraethylammonium chloride(TEA) and 0.1 ㎎/㎖ EK extract was added.
To analyze the effect of the EK extract on influx of extracellular calcium chloride(Ca2+) in rabbit carotid artery, in Ca2+-free krebs solution, krebs solution containing 1 mM Ca2+ was infused into the contracted arterial ring by NE after pretreatment of EK extract.
To measure the cytotoxicity of the EK extract, cell viability of human umbilical vein endothelial cell(HUVEC) was measured by MTT assay, and nitric oxide(NO) was measured by Griess reagent.

Results : The EK extract significantly relaxed the arterial ring with intact endothelium contracted by NE, but the vasorelaxation effect of the EK extract was inhibited in the arterial rings with damaged endothelium.
The vasorelaxation effect of the EK extract was not different between the IM-pretreatedand and non-treated arterial rings.
The vasorelaxation effect of EK extract were significantly inhibited, when arterial rings were pretreated with L-NNA, TEA, MB.
And in Ca2+-free krebs solution, increasing of arterial contraction by Ca2+ addition were also inhibited by the treatment of EK, but not significant.
The treatment of EK extract increased NO concentration in HUVEC.

Conclusions : This study suggested that the vasorelaxation effect of EK extract would be related with EDHF and NO production and increasing of cyclic GMP.