Abstract: Objective To explore the effects of sodium arsenite(NaAsO₂) on the protein expression of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and Nrf2-regulated dow nstream anti-oxidant enzymes in Chang liver cells.Methods Chang liver cells were treated with NaAsO₂ (25 mol/L) for 2,4,6,12,and 24 hours or NaAsO₂ at different doses of 10,25,and 50 mol/L for 6 hours.Western blot assay was used to detect the protein expression of Nrf2,NAD(P) H:quinone oxidoreductase(NQO1),and heme oxygenase-1(HO-1).Results NaAsO₂ exposure of 25 μmol/L could significantly induce Nrf2,NQO1,and HO-1 protein expressions in Chang liver cells.Nrf2 protein level was higher than control cells 2 hours after NaAsO₂ exposure and approached the peak 4 hours after the exposure.NQO1 protein level increased from 4 to 24 hours after the exposure.The protein expression of HO-1 was induced 6 hours after the exposure with a time-effect response.When the cells were treated with 10,25,and 50 μmol/L of NaAsO₂ for 6 hours,dose-effect response was observed.Conclusion NaAsO₂ could increase protein expression of Nrf2,NQO1,and HO-1 in Chang liver cells with a dose-effect response.