Aim To explore the changes in extracellar signal-regulated prote in kinase(ERK1 /2) in endothelial cell induced by Angiotensin Ⅱ at the different time courses,and its possible molecular mechanism.Method s Human umbilicalve in endothe-lial cell(HUVEC) were cultured in vitro and intervened by AngⅡ.HUVEC were divided into 2 groups,the control group,AngⅡ group(stimulated by AngⅡ10-6mol/L for 24h).Flow cytometery with Annexin V-FITC /PI double staining and Hoechst33258 fluo-rescence staining were used to detect apoptosis of HUVEC.The expressions of apoptosis-association genes Bcl-2,Bax were detected by RT-PCR and ERK1 /2 levels were detected by Western-blotting at different time points.Results 10-6mol/L Angiotensin Ⅱ stimulation stimulated cell apoptosis.Bcl-2mRNA levels were time-dependently decreased,the radio of Bcl-2 /Bax was decreased markedly(p<0.05).Phosphorylation of ERK1 /2 began to increase and reach the peak at 18 h(p<0.01).Conclusions Cell apoptosis is possibly important factor for atherosc lerosis.One of its molecular mechanisms might be associated with decreasing the expression level of Bcl-2 and the radio of Bcl-2 /Bax.There is a probability that activated ERK1/2 signal pathway is involved in the process of pathologic and physiologic reaction in the apoptosis of endothelial cell induced by Angiotensin Ⅱ.