青蔥(Allium fistulosum L., Alliaceae) 為本省重要香辛料蔬菜，也是中國菜中最經常使用之香辛料之一。許多研究指出蔥屬植物，例如：大蒜、洋蔥之香味成分對心血管疾病具特殊之生理效應。已知餵食生蔥汁能降低雄性正常血壓鼠(Sprague-Dawley, SD)或自發性高血壓鼠(Spontaneously hypertensive rat, SHR)之收縮血壓，生蔥與熟蔥水萃取物更可藉由NO-cGMP路徑降低體外試驗之血管張力。為進一步了解青蔥水萃物對於降低人體血管壓力之真實功效，故本實驗利用不同濃度之青蔥水萃取物(0~3.2 mg/ml)刺激人類臍靜脈內皮細胞(human umbilical vein endothelium cell, HUVEC)，觀察內皮衍生性一氧化氮(endothelium-derived nitric oxide, EDNO)及環化鳥核甘單磷酸(cyclic GMP)之生合成，並於不同處理時間，探討對一氧化氮合成酶(endothelial nitric oxide synthase, eNOS)之影響。實驗結果發現：(1) 不同濃度之青蔥水萃取物可誘導細胞產生cGMP；(2) 青蔥水萃取物誘導而產生之cGMP可被Nω-Methyl-L-arginine acetate (LNMA)所抑制；(3)利用西方墨點法測定 eNOS之蛋白質表現，以濃度0.2mg/ml之青蔥水萃取物之效果最為顯著；(4) 利用西方墨點法測定eNOS之蛋白質表現，以10分鐘處理之效果最為顯著。 Welsh onion(Allium fistulosum L., Alliaceae) is one of the important flavoring vegetables in Taiwan, and it is often used in Chinese dishes. Many studies have found that the flavor compounds of Allium species, especially onion and garlic, have special physiological effects on cardiovascular disease. In our hands, we have found that chronic feeding of Welsh onion extracts can lower systolic blood pressure and prolong the bleeding time in both normotensive Sprague-Dawley (SD) rats and Spontaneously hypertensive rat (SHR). In vitro study, the Welsh onion extracts exert their vasorelaxing effects via the NO-cGMP pathway. Whether Welsh onion can modulate vascular tone and act as a hypotensive agent in human is still unknown. In this study, we investigated the different concentrations (0~3.2 mg/ml) of Welsh onion extract on the effects of stimulate human umbilical vein endothelium cell (HUVEC) for released the endothelium-derived nitric oxide (EDNO) and cyclic GMP, and the effects of the endothelial nitric oxide synthase (eNOS) at various incubation time. Our results indicated : (1) Different concentrations of Welsh onion extracts could increase the cGMP production in endothelial cells. (2) Welsh onion extracts elevated cGMP level, which could inhibit by Nω-Methyl-L-arginine acetate (LNMA). (3) Welsh onion extracts with the concentration of 0.2 mg/ml significantly increased the protein expression of eNOS that determined by Western blotting. (4) Welsh onion extracts with the incubation time of 10 min significantly increased the protein expression of eNOS that determined by Western blotting.