Metallothioneins MTs that are intracellular
Metallothioneins (MTs) that are intracellular proteins responsible for the maintenance of metal homeostasis are involved in arsenic toxicity (Kita et al., 2006). Four major MT isoforms have been reported so far, MT1, MT2A, MT3 and MT4. The synthesis of MT1 and MT2A isoforms in mammal cells can be induced by a variety of factors including environmental exposures. The detoxification processes include the nigericin of the metal and assist with their transportation and extraction of the cell (Kayaalti and Soylemezoglu, 2010).
Material and methods
Discussion The results of the present study showed Astotal evaluated in several aquifers used as drinking water range from 10 to 96 μg/L and were on average three-fold greater than WHO's drinking-water guideline of 10 μg/L while the highest concentrations were found in the rural area of Mamoncito in Margarita municipally which were on average eight-fold higher than this guideline ranging from 17 to 96 μg/L. In general, all drinking-water wells analyzed exceeding the WHO guideline. The arsenic concentrations of groundwater measured in the present study were comparable with those from other Latin-American sites, on average from 4.49 to 43.3 μg/L in Mexico (Meza et al., 2004), from 0.6 to 36.8 μg/L in Chile (Caceres et al., 2005), from 0.5 to 189 μg/L in Argentina (Concha et al., 2006), 72 μg/L in Bolivia (Ormachea-Muñoz et al., 2013), and from 0.1 to 67 μg/L in Peru (George et al., 2014). LADD and HQ have been reported in the literature as an important human risk tool as exposure assessment for many pollutants (Rasool et al., 2016). LADD was 0.31 μg/kg-weight/day and HQ was above the 1. Thus, the study population in Colombia have been chronically exposure to arsenic above the permissible concentrations by drinking groundwater. In our study, we found a moderated but positive correlation between total arsenic concentrations in groundwater used for drinking water, Astotal and total arsenic concentrations excreted in urine, TuAs (r = 0.61; p = 0.000). When the total arsenic concentrations in groundwater was adjusted as total arsenic intake per day and per kg bodyweight (μg/kg body weight/day) or LADD (lifetime average daily dose exposure of As) and correlated with arsenic concentration excreted in urine (TuAs), the coefficient correlation was greater and significant (r = 0.68; p = 0.000). Thus, it demonstrated clearly that urine was a biomarker of arsenic exposure in our study population. Similar positive and statistical significant correlation trends were reported between arsenic exposure versus arsenic urinary excretion (Meza et al., 2004; Concha et al., 2006; Middleton et al., 2016). In general, DMA is the major arsenic metabolite excreted after exposure to arsenic via drinking water, follow by InAs, and MMA; typically reported in the literature on averages in the ranges of 60–80%, 10–30%, 10–20%, respectively (Vahter, 2000; Loffredo et al., 2003; Mandal et al., 2001). DMA was variable but it was the dominant methylated arsenic species measured in the urine samples, with 54.8% however, was slightly lower than mentioned range. While some authors (Hsueh et al., 2002; Middleton et al., 2016) indicate that DMA is usually between 60 and 80% of total As, in our study this outcomes has been a little lower. Probably a lower degree of methylation in the urinary excretion of the studied population is due to the considerable presence of some glutathione s-transferase polymorphisms associated with the oxidative methylation of inorganic arsenic. Several authors also have reported lower values for DMA (Meza et al., 2004), and MMA (Vahter et al., 1995; Concha et al., 2006). On the contrary, MMA and InAs (AsIII and AsV) were 18.3% and 25.3% in the expected ranges of 10–30%. Although AsIII is usually the only inorganic arsenic species found in urine, there are some studies that indicate that AsV may be also present. Middleton et al., 2016, indicated that urine samples from a population drinking from water supply with high As content, presented mean concentration of AsV of 0.5 ranging from