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Objective To investigate the impairment mechanism of learning and memory function induced by arsenite exposure through studying the effects of sodium arsenite on gliotransmitter release from astrocytes.Methods Primary cultured astrocytes were isolated from neonatal (0-3 days) Wistar rats and determined by glial fibrillary acidic protein (GFAP) immunofluorescence staining.The primary cultured astrocytes were randomly divided into four groups,in which astrocytes were exposed to 0.0,2.5,5.0,or 10.0 μmol/L sodium arsenite,respectively,for 24 h.Intracellular free Ca2+ concentration ([Ca2+]i) in astrocytes was measured by fluorescence dual wavelength spectrophotometer;,concentrations of glutamate,D-serine,glycine and γ-aminobutyric acid were measured by high performance liquid chromatography (HPLC).Results More than 95％ cells were positive for GFAP immunofluorescence staining.The difference of [Ca2+]i among groups treated with sodium arsenite was statistically significant (F =20.030,P ＜ 0.05).[Ca2+]i increased significantly in group treated with 10.0 μmol/L sodium arsenite [(263.27 ± 14.80)nmol/L] compared with those in groups treated with 0.0,2.5,5.0 μmol/L sodium arsenite [(204.24 ± 27.21),(214.49 ± 21.85),(232.74 ± 23.14)nmol/L,all P ＜ 0.05].The differences of the levels of D-serine,glycine and γ-aminobutyric acidamong groups treated with sodium arsenite were significant (F =26.599,33.539,5.599,all P ＜ 0.05).The levels of D-serine [(21.580 ± 1.313),(21.936 ± 1.539),(23.401 ± 1.648)μmol/L],glycine [(26.353 ± 2.449),(29.711 ± 1.530),(29.234 ± 2.057)μmol/L] and γ-aminobutyric acid [(27.277 ± 3.421),(30.213 ± 2.098),(29.364 ± 2.588)μmol/L] released by astrocytes increased significantly in groups treated with 2.5,5.0,10.0 μmol/L sodium arsenite compared with those in groups treated with 0.0 μmol/L sodium arsenite [(16.017 ± 1.046),(16.763 ± 3.007),(22.736 ± 4.139)μmol/L,all P ＜ 0.05].Conclusion Arsenite could affect gliotransmitter release from astrocytes,and further impair learning and memory function.
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Objective To explore the intellectual effects of arsenic in drinking water on children. Methods Intellectual effects were evaluated by computer-based reaction time and Combined Raven's Test. Children aged 9 to 11 years living in three villages of Inner Mongolia were investigated in April, 2006. The arsenic concentrations in the drinking water of the three villages were 0.16 mg/L, 0.09 mg/L and less than 0.05 mg/L (control group). Results The mean, fastest and slowest visual reaction time of children exposed to the high levels of arsenic through drinking water were longer than those of children in control. The differences of mean, fastest and slowest visual reaction time between girls exposed to 0.16 mg/L arsenic and control were significant; the differences of the mean and slowest visual reaction time between 10-year old children exposed to 0.16 mg/L arsenic and control were significant. IQ of girls exposed to 0.16 mg/L arsenic was significantly lower than that in control. Conclusion Intellectual function of children can be affected by arsenic in drinking water, and the intellectual effects of arsenic on girls are more obvious.
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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 ( P
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Objective To explore the effects of exogenous glutathione on arsenic distribution and nitric oxide (NO) metabolism in the brain of mice exposed to arsenite through drinking water. Methods Female Kunming mice were randomly divided into 5 groups, eight in each, and the mice were exposed to sodium arsenite through drinking water at doses of 0 mg/L (control) and 50 mg/L arsenic for 4 consecutive weeks, on the fourth week, with the exposure of arsenic, glutathione was given through intraperitoneal injection at doses of 200 mg/kg b.w, 400 mg/kg b.w or 800 mg/kg b.w, respectively for 7 days. In the end of treatment, the samples of blood and brain were collected. Levels of inorganic arsenic (iAs), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA) were determined by HG-AAS method. Activities of nitric oxide synthase (NOS) and the concentrations of NO were determined with kits. Results Compared with those in single arsenic group, glutathione significantly decreased levels of iAs, MMA and total arsenic levels (TAs) in the blood and levels of DMA and TAs in the brain. Activities of NOS and levels of NO in As group were significantly lower than those in control, however administration of glutathione could ameliorate these toxic effects, and NOS activities in groups treated with 400 mg/kg b.w and 800 mg/kg b.w glutathione were significantly higher than those in single arsenic group. Conclusion Exogenous glutathione may promote methylation of arsenic, therefore reduce arsenic levels in both blood and brain. Moreover, it is proposed that administration of exogenous glutathione can ameliorate the adverse effects of arsenic on NO metabolism in the brain via decreasing the brain arsenic burden.
