![]() GSTO (ω class) omega 1 reduces pentavalent and methylated arsenic species. Four members from the GST family including GSTO (isoforms 1 and 2), GSTP1, GSTT1 and GSTM1 could influence the capacities to metabolize arsenic, according the expression level and the presence of different allele variants. PNP enzymes has been proposed as reducing agents of As V, expression of As3MT probably plays an important role in the methylation of As III, and GST are a series of phase II enzymes that detoxify xenobiotics via conjugation reaction with glutathione (GSH). The main enzymes involved in the arsenic metabolism are classified in three groups: purine nucleoside phosphorylase (PNP), arsenic methyltransferase (AS3MT), and glutathione-S-transferases (GSTs), all of them having genetic polymorphisms. The presence of arsenic in soils and waters naturally may occur, although anthropogenic activities have been the main contributory factor to the environmental contamination by arsenic, soils naturally enriched by arsenic need more attention. Reports in several countries of Latin America have shown concentrations of arsenic in groundwater above this risk level and the distribution of arsenic in soils, sediments, vegetables and irrigation water has been recently reviewed in Colombia and Brazil. The World Health Association has recommended a safe level of 10 µg/L as a guideline in drinking water. Inorganic arsenic species are classified by the International Agency for Research on Cancer as Group I type compounds. The As III corresponds to arsenite species: AsO 3 3−, HAsO 3 2−, H 2AsO 3 - and H 3AsO 3 while As V denotes arsenate species: AsO 4 3−, HAsO 4 2−, H 2AsO 4 − and H 3AsO 4. The exposure to inorganic arsenic species (InAs) such as trivalent (As III) and pentavalent (As V) through drinking groundwater is a global public health issue leading to chronic toxicological effect in humans. Interactions between polymorphic variants As3MT* GSTM1 and GSTO2*GSTP1 could be potential modifiers of urinary excretion of arsenic and covariates as age, LADD, and alcohol consumption contribute to largely vary the arsenic individual metabolic capacity in exposed people. Multivariate analyses showed statistically significant association among interactions gene-gene and gene-covariates to modify the MMA and DMA excretion. Both DMA and MMA concentrations were higher in GSTM1-null genotypes compared to the active genotype. Besides, DMA concentrations were lower in heterozygous and/or homozygous genotypes of GSTP1 compared to the wild-type genotype. Univariate analyses among arsenic metabolites and genetic polymorphisms showed MMA concentrations higher in heterozygous and/or homozygous genotypes of As3MT compared to the wild-type genotype. The median of total arsenic concentration in groundwater was of 33.3 μg/L and the median of LADD for the high exposure dose was 0.33 µg/kg bw/day. The influence of polymorphic variants, LADD and other factors were tested using multivariate analyses. Arsenic metabolites: As III, As V, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured using HPLC-HG-AFS. In addition, genetic polymorphisms ( GSTO2-rs156697, GSTP1-rs1695, As3MT-rs3740400, GSTT1 and GSTM1) were evaluated by real time and/or conventional PCR. ![]() Surveys on 151 participants aged between 18 and 81 years old were applied to collect demographic information and other factors. Twenty-two groundwater wells for human consumption from municipalities of Colombia were analyzed for assessed the exposure by lifetime average daily dose (LADD) (µg/kg bw/day). We assessed the influence of polymorphic variants of Arsenic-3-methyl-transferase and Glutathione-S-transferase on urinary arsenic metabolites. The urinary arsenic metabolites may vary among individuals and the genetic factors have been reported to explain part of the variation.
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