Abstract: Objective To study the effects of homocysteine(Hcy)at different concentrations on expressions of endothelial nitric oxide synthase(eNOS)and caveolin-1 mRNA and protein in cultured human umbilical vein endothelial cells(HUVECs)in base and calcium ionophore activated state.Methods HUVECs were divided into four groups:control group,Hcy groups(at different concentrations of 20,50,100,and 300μmol/L),A23187 group(1μmol/L),and Hcy(at different concertrations of 20,50,100,and 300μmol/L)+A23187 group.After cultured for 24 hours,the expressions of eNOS and caveolin-1 mRNA and protein,nitric oxide(NO),malondialdehyde(MDA)content,eNOS,and superoxide dismutase(SOD)activity were detected.Results The expressions of caveolin-1 were 1.13 in control group and 0.21-2.05 in Hcy groups with a dose-dependent trend(P<0.05).The expression of eNOS mRNA was between 1.80-2.08,without differences among the groups(P>0.05).The eNOS and NO were 1.20 U/mL and 122.41μmol/L in the control group and 0.65-0.74 U/mL and 65.33-98.91μmol/L in Hcy groups,with dose-dependent trends(P<0.05).Conclusion There is no relationship between decreased activity of eNOS induced by Hcy and eNOS expression.Hcy may increase the association of caveolin-1 and eNOS by enhancing the expression of caveolin-1 in HUVEC both in base and activated state,which could decrease the activity of eNOS.