Objective To study the dose-dependent effect of sodium arsenite on the expression of p53 gene in human embryonic lung fibroblasts(HELF)in vitro.Methods The human embryonic lung fibroblasts were divided into four groups in vitro based on completely randomized design.The expression of p53 mRNA was detected by real-time PCR and the expression of p53 protein was detected by immunohistochemical SAB,respectively,in human embryonic lung fibroblasts which were exposed to different doses(0,3,9 and 15?mol/L)of sodium arsenite for 24 hours.The one-way analysis of variance and post hoc comparisons were performed for testing the differences among groups and the linear correlation was for testing correlation between doses and the expression of p53 gene.Results Compared with that of exposure to 0?mol/L sodium arsenite,the expression of p53 mRNA in HELF was increased significantly(P0.05).The p53 mRNA expression was increased in dose-dependent manner with the increased concentration of sodium arsenite(r=0.947,P