Effects Of Exogenous GSH On Metabolism Of Inorganic Arsenic, Glu And NO In Mice Exposed To Arsenite Through Drinking Water

Endemic arsenic poisoning of drinking-water type is one of major endemic diseases in our country.Water arsenic is the major ingested pathway for population of arsenic exposure.Inorganic arsenic(iAs) is the main arsenic speciation in drinking water. Methylated metabolism of iAs occurs in the liver.Then,methylated metabolites enter in bloods.Furthermore,they distribute on the other tissues and organs from blood circulation.End products of arsenic metabolism are pentavalent dimethylarsenic acid (Dimethylarsinic acid,DMA~V).The toxicity of DMA~v is significantly lower than that of iAs and trivalent monomethylarsonous acid(Monomethylarsonous acid,MMA~Ⅲ). Thus,the capability of arsenic methylation in liver determins the arsenic speciation in other tissues and organs,and effects toxicity of arsenic in different tissues and organs.Arsenic on the toxic effect of central nervous system has aroused widespread concern.Glutamic acid(Glutamate,Glu) is an important excitatory neurotransmitter of mammalian higher nervous activity in the central nervous system.The abnormality of Glu levels can cause higher nervous activity into disorder.Glutamine synthetase(GS) is the key enzyme of Glu metabolism.Nitric oxide(NO) is an important messenger molecule in the central nervous system.NO regulates neuron on the response of excitatory amino acids.Nitric oxide synthase(NOS) is the key enzyme of NO metabolism.It is seems that arsenic has an effect on level ofGlu and NO,and also has effect on enzyme activity and the toxicity of central nervous system.Arsenic is a sulfophilic element.Arsenic exposure can cause endogenous GSH levels decrease, resulting in oxidative damage of organism.This study,we give exogenous GSH to mice exposed to arsenic through drinking water.To explore the effect of GSH on methylated metabolism of arsenic in vivo.and further to explore the effect of GSH on arsenical toxicity in brains.As the guidance of endemic arsenic poisoning,we provide experimental evidences for prevention and treatment in China.Materials and Methods1.Animals and GroupsSelect female and healthy mice,whose weights are between(25.0±2.0)g.After adaptive environment,the animals were randomly divided into 5 groups of 8 animals each.The mice were randomly divided into control group(Con),arsenic group(As), GSH-low-dose group(GSH-L),GSH-middle-dose group(GSH-M) and GSH-high-dose group(GSH-H) in combination,respectively.2.ChemicalsUse sodium arsenite to poison.Mice were exposed to arsenite by drinking water for 4 weeks and the concentrations of iAs~Ⅲwere 50mg/L or untreated drinking water (control group).Use glutathione to interfere.And mice were injected intraperitoneally with different concentrations of GSH(200,400,or 800 mg/kg weight) about seven days starting from the fourth week.After etherization,blood samples were taken from eyeballs and brains,livers were extracted immediately,stored at -40℃.3.Methods(1) The concentrations of different species of As in livers,bloods and brains-hydride generation-cold iron capture-atomic absorption spectrophotometry.(2) The activities of glutamine synthetase - the formation ofγ-glutamyl hydroxamate by the absorbance of the solution at 535nm.(3) The concentrations of glutamate - kits produced by Nan jing jian cheng.(4) The activities of nitric oxide synthase - kits produced by Nan jing jian cheng.(5) The concentrations of nitric oxide - kits produced by Nan jing jian cheng.(6) The concentrations of proteins - biuret method.(7) The concentrations of glutathione - DTNB method.4.StatisticsThe data were input into computers,analyzed and treated by the SPSS 13.0.The concentrations of different species of As in blood and brain did not show the normal distribution,so using the Kruskal-Wallis test.Other index were analyzed by analysis of variance(ANOVA). ResultsContents of iAs,MMA and DMA in livers,bloods and brains were significantly increased in arsenic group The activity of GS and NOS and the concentrations of NO were significantly decreased in arsenic groups compared with control,but the concentrations of Glu increased in arsenic groups.The concentrations of iAs,MMA and DMA in each dose group of GSH were decreased compare with the As group in brains and bloods of mice.The concentrations of DMA had no significant differences among three dose group of GSH in livers.The concentrations of DMA in GSH-H group were significantly higher than them in GSH-M group in bloods(P＜0.05),which had no significant differences with GSH-L group.The primary methylated index(PMI) and secondary methylated index(SMI) in GSH-H group were markedly higher than them in GSH-L group in livers(P＜0.05).The SMI in GSH-H group was significantly higher than them in GSH-L and GSH-M groups in bloods(P＜0.05).The levels of glutathione in GSH-H group were significantly higher than them in GSH-L and GSH-M groups in livers(P＜0.05).The activity of TNOS and the concentrations of NO in GSH-H group were significantly higher than them in arsenic group in brains(P＜0.05).The activity of GS and the concentrations of Glu in three dose groups had no significantly differences in arsenic group in brains.Conclusions1.Given exogenous GSH could promote the methylated metabolism of iAs~Ⅲand turn it into MMA and DMA in mice.Furthermore,the concentrations of iAs were decreased in organs and tissues.Moreover,toxical impairments iAs are decreased for health of organisms.2.Given exogenous GSH could promote the methylated metabolism of iAs~Ⅲin livers.To increase the speed of methylated metabolism of arsenic in vivo.Furthermore, the concentrations of iAs were decreased in bloods.3.Given exogenous GSH could decrease the concentrations of arsenic speciation, and could further improve the adverse effect of arsenic on metabolism of NO in brains.4.Given exogenous GSH could promote the concentrations of GSH in livers and bloods.The exogenous GSH was helpful to improve oxidative stress in brains.