Selenium–Mercury Interactions in Man and Animals

Abstract

Selenium-mercury interactions were most extensively studied in relation to alleviation of Hg toxicity by added selenium. This presentation considers the influence of mercury on endogenous selenium, on its tissue and cellular "status" after lifelong or acute exposure to mercury vapor (Hg o). Discussed are data obtained from (1) humans living near or working in a mercury mine, and (2) rats experimentally exposed in the mine. Mercury vapor is unique--or similar to methylmercury--because of its ability to penetrate cell membranes and so invade all cells, where it is oxidized in the biologically active form (Hg++) by catalase. Such in situ-generated ions can react with endogenously generated highly reactive Se metabolites, like HSe-, and render a part of the selenium unavailable for selenoprotein synthesis. Data on human populations indicate that in moderate Hg exposure combined with an adequate selenium supply through diet, Se bioavailability can be preserved. On the other hand, the results of an acute exposure study emphasize the dual role of selenium in mercury detoxification. Besides the well-known Se coaccumulation through formation of nontoxic Hg-Se complexes, we observed noticeable Se (co)excretion, at least at the beginning of exposure. The higher Hg accumulation rate in the group of animals with lower basal selenium levels can also point to selenium involvement in mercury excretion. In such conditions there is a higher probability for decreased selenoprotein levels (synthesis) in some tissues or organs, depending on the synthesis hierarchy.

Factors in Fish Modifying Methylmercury Toxicity and Metabolism

“…Much of this elevation in Hg and Se persisted long after animals were switched from a high MeHg diet to a basal diet. Although the form of Hg was not determined, our results are consistent with deposition of a long-lived complex of Se with inorganic Hg rather than MeHg, based on the work of others where long-lived inorganic Hg accumulation was demonstrated in cats and primates, as well as humans [8,17,21,22]. The increase in Hg was accompanied by an increased level of Se, often in a Hg/Se molar ratio between 1 and 2.…”

Levels of Heavy Metals in Canned Bonito, Sardines, and Mackerel Produced in Turkey

“…This mechanism involves the reaction of mercury with selenium, which is an essential trace element [44,45]. The protective effects of selenium against mercury toxicity have been demonstrated in many animals and in humans [46,47]. Therefore, selenium concentration must also be considered when Hg concentration is high or above the limits.…”

Biological responses related to agonistic, antagonistic and synergistic interactions of chemical species

“…In addition, the detection of the Se II -PC 2 complex and Se-cysteinylserine glutathione in Thunbergia alata suggested that symptoms of increased toxicity may have been due to the competition of Se II with As III for sulfhydryl groups, which are crucial to arsenite detoxification in plant cells [59]. A Zebrafish Se reduces visual deficits due to developmental Hg exposure [74] A Diatoms and mussels Se significantly inhibits the uptake of Hg [196] SeProt/ Hg 0 A Humans Se detoxifies Hg [197] SeProt/MeHg + A Human cells Hg induces a "selenium-deficient-like" condition [136] A Mice Hg affects the activities of selenoenzymes [71] Interactions of selenium-and sulfur-containing species Se species/S species A Bacterial systems Se appears to use the sulfur enzymatic system [79] A Se-hyperaccumulator plant Important differences between S and Se biochemistries [ A antagonism, S synergism, SeMet selenomethionine, SeProt selenoproteins, MeHg + methylmercury, SeBet selenobetaine, iAs(III) AsO 3 3− or AsO 2…”