Abstract: Objective To observe sodium arsenite(NaAsO₂)-induced expression of heme oxy genase-1(HO-1)in bovine aortic endothelial cells(BA EC).Methods Cultured BA EC was exposed to NaASO2(0~15 Lmol/L)for 0~24 h,respectively.Western blot was used to detect the induction of HO-1 protein.Results 0.5 μmol/L NaAsO₂ exposure induced the pro duction of HO-1 protein sig nificantly,with dose-dependent and time-dependent relationship.Low dose of NaAsO₂(2.5 Lmol/L)could induce markedly the expression of HO-1 protein.Conclusion HO-1 induction could be a cellular stress respo nse,and has potential for being used as a sensitive biomarker forinorg anic arsenic exposure,which may be useful for fur ther research of the biological response of arsenic.