ObjectiveTo investigate the effect of naphthalene acetic acid (NAA) on proliferation and apoptosis of mice hepatocytes.MethodsFifty mice were randomly divided into five groups: positive control, normal control, low, middle and high dose of NAA groups.Mice in low, middle and high dose of naphthalene acetic acid groups were fed with 200 mg/kg, 1 000 mg/kg and 5 000 mg/kg NAA animal food, respectively.Mice in positive control, normal control groups were fed with usual animal food.After 4 weeks, mice were sacrificed and liver was separated.Three days before scarification, mice in positive control group were given 20 mg/kg ascyclophosphami daily by intraperitoneal injection.The proliferative activity of hepatocytes was detected by MTT assay.The expressions of PCNA protein and Caspase-3 were measured by immunohistochemistry method.ResultsThe proliferative activities of mice hepatocytes in high dose group and normal control group were 0.794±0.019 and 1.055±0.019, respectively.The expressions of PCNA protein and Caspase-3 in high dose group were 11.2% and 37.9%, and those in the normal group were 33.1% and 6.3%, respectively.All differences were significant (P＜0.01).ConclusionHigh dose of NAA acid could significantly inhibit proliferation and increase apoptosis of hepatocytes in mice.