Abstract: ObjectiveTo analyze the association between the level of arsenite or arsenate and its metabolites and the activity of methyltransferases,and to explore the relationship between arsenic’s metabolism and toxicity.MethodsForty-two female Wistar rats were devided into 7 groups(normal control group;high,moderate,and low arsenite groups and high,moderate,and low arsenate groups).After the animals were treated for three months,the liver were collected rapidly after the sacrifice and saved in a refrigerator.High efficiency liquid chromatography and hydride genesis atomic fluorescence spectroscopy(HPLC-HGAFS) were used to determine speciation and concentrations of arsenate and arsenite and their metabolites in liver of the rats,and the activity of methyltransferases in the liver was determined.Meanwhile the correlation between the level of arsenic metabolites and the activity of methyltransferases was examined.ResultsThe contents of iAs³⁺ for the rats in high,moderate,and low arsenite groups(255.9±58.6,61.1±10.2,and 62.6±17.3 ng/g) were significantly lower than those in arsenate groups(P<0.05 for all).The contents of dimethylarsinic acid(DMA) in the rats of high,modrate,and low arsenite groups(2 663.2±203.7,118.4±24.2,and 143.5±34.1 ng/g)were significantly lower than those in arsenate groups(P<0.05 for all).Meanwhile,the activity of methyltransferases in high,moderate,and low arsenite groups(4.81±0.25,2.32±0.41,and 1.82±0.25 μg/s·mg)were significantly lower than those in arsenate groups(P<0.05 for all).The activity of methyltransferase in liver correlated positively with the content of DMA and monomethylarsonic acid(MMA) by Spearman methods(P<0.01),with the correlation coefficients of 0.594 and 0.497,respectively.ConclusionBoth arsenate sodium and arsenite sodium could increase(or decrease) the level of MMA and DMA by enhancing(or restraining) the activity of methyltransferase in liver,which would lead to different toxicity.