Metallomic Approach to Mercury and Selenium in the Liver Tissue of Psectrogaster amazonica and Raphiodon vulpinus from the Brazilian Amazon

This paper reports the results of a mercury (Hg) and selenium (Se) metallomic study in the liver tissues of <i>Psectrogaster amazonica</i> and <i>Raphiodon vulpinus</i> from the Brazilian Amazon. Two-dimensional electrophoresis, graphite furnace atomic absorption spectrometry, and liquid chromatography-tandem mass spectrometry were performed. Hg and Se determinations allowed the calculation of Hg:Se and Se:Hg molar ratio and Se values for health benefits (Se HBVs). The Se:Hg values were >1 for both fish species, whereas the Se HBVs were >5 for <i>P. amazonica</i> and >10 for <i>R. vulpinus</i>, indicating that both possess Se reserves to control Hg toxicity. The metallomic data allowed the identification of 11 Hg/Se-associated protein spots in the two fish species, with concentrations in the range of 9.70 ± 0.14 and 28.44 ± 0.31 mg kg^-1 of Hg and 16.15 ± 0.21 and 43.12 ± 0.51 mg kg^-1 of Se. Five metal binding proteins (<i>MBP</i>) in the Hg/Se-associated protein spots in the liver proteome of <i>P. amazonica</i> and eight in <i>R. vulpinus</i> were identified, indicating the possible formation of Hg/Se complexes on the <i>MBP</i> structures. The activities analysis of catalase, superoxide dismutase, GPx enzymes, and lipoperoxide concentrations demonstrated that Hg-induced oxidative stress did not occur, possibly because both fish species possess Se reserves necessary to inhibit the Hg's deleterious effects.