Abstract: Objective To analyze the difference in distribution of arsenic metabolite in liver of the rats treated with arsenite and arsenate,and to explore metabolism and toxicity of arsenic.Methods Seventy-two Wistar rats were devided into 7 groups.After three months' treatment,the liver samples of the rats were collected and kept in deep freeze refrigerator.With high efficiency liquid chromatography and hydride genesis atomic fluorescence spectroscopy(HPLC-HGAFS),the speciation and concentrations of arsenate and arsenite and their metabolic products in the liver were determined.Meanw hile,the recovery rate of monomethylarsonic acid(MMA) was determined to estimate the accuracy of the results.The arsenic accumulation was evaluated based on the content of total arsenic in liver and the differences in pathway and capability of methylation were estimated according to levels of primary methylated index(PMI) and secondary methylated index(SMI) of arsenic in the liver.Results There were significant differences in the levels of total arsenic between high,moderate,and lowarsenite groups(1 142.9±50.4,484.6±37.4,323.3±20.2 ng/g wet weight) and between high,moderate,and low arsenate groups(3 695.2±345.9,1 833.8±229.6,1 170.5±77.4 ng/g wet weight) (P< 0.05 for all).Except high dose group,the level of iAs³⁺ (118.4±23.9,252.3±14.3 ng/g wet weight) and dimethylarsinic acid(DMA) (353.2±45.6,55.2±10.6 ng/g wet weight) in the liver of moderate and low arsenite group were lower than the level of iAs³⁺ (558.7±39.0,759.5±67.6 ng/g wet weight) and DMA (1269.7±219.9,402.1±60.5 ng/g wet weight) in moderate and low arsenate groups(P< 0.05).The level of MMA(13.0±2.88,15.8±3.14 ng/g wet weight) in the liver of moderate and low arsenite group were higher than the level of MMA (5.35±1.18,8.87±1.66 ng/g wet weight) of the moderate and low arsenate groups(P< 0.05).The level of PMI and SMI of different arsenite group in the liver were lower than the same dose arsenate groups(P< 0.05).Conclusion The accumulation of pentavalent arsenic metabolite is more than that of trivalent arsenic in the liver of rats.In the liver the primary and secondary methylation of pentavalent arsenic is more intensive than that of trivalent arsenic and with stronger hepatic toxicity in rats.