Effects of Exogenous Methionine on Arsenical Distribution in Female Mice Exposed to Sodium Arsenite through Drinking Water

Objective To explore the effects of exogenous methionine on arsenical distribution in liver,blood and brain of mice exposed to sodium arsenite through drinking water. Methods The female Kunming mice were randomly divided into control group, the alone arsenic exposure group , the low level methionine intervention group, the moderate level methionine intervention group and the high level methionine intervention group, eight mice in each group . The mice in the experimental groups were exposed to sodium arsenite through drinking water at 50 mg/L arsenic for four consecutive weeks. And at the fourth week the 5 groups were treated intraperitoneally with saline solution (control and As group),100 mg/kg b.w,200 mg/kg b.w or 400 mg/kg b.w methionine,respectively . Twenty-four hours after cessation of methionine administration,mice were anaesthetized and rapidly dissected. The samples of blood,liver and brain were removed immediately for arsenic species analysis. Levels of inorganic arsenic (iAs),monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA) were determined by HG-AAS method. Then total arsenic speciation( TAs), primary methylation ratio( PMR)and secondary methylation ratio( SMR)in each tissue were calculated. Results Compared with the control group, the levels of iAs, MMA, DMA and TAs in liver, brain and blood, were significantly higher in all experimental groups ( P0.05). Compared with those in mice exposed to arsenite alone,levels of DMA and PMR in the moderate and high level methionine groups were significantly higher in liver( P0.05) ;levels of iAs,MMA and TAs in blood in all methionine intervention groups were much lower ( P0.05) ; and levels of DMA and TAs in all the methionine intervention groups were significantly decreased in brain (P0.05). Conclusion Exogenous methionine can regulate arsenic methylation in liver,and promote excretion of methylated arsenic,therefore reduce arsenic levels in both blood and brain.