Selenium protection against mercury toxicity

Sugiura, Y., Y. Hojo, Y. Tamai, and H. Tanaka. 1976. Selenium protection against mercury toxicity. Binding of methylmercury by the selenohydryl-containing ligand.. Amer. Chem. 98 2339-2341. 

Antagonism The effect of mixture is less than that estimated for additivity on the basis of the toxici-ties of the components. The protection against mercury toxicity by selenium is a typical example of this category. This group is further classified into inhibition - a component does not have effect and decreases the effect of another component or other components and masking - one component overrides the effect of other. 

Selenium protects against the toxic effects of arsenic, cadmium, copper, mercury, and silver. Likewise, these elements counteract the toxic effects of selenium. 

Methylmercury and other mercury compounds have a strong affinity for sulfur and selenium. Although selenium has been suggested to provide protection against the toxic effect of methylmercury, no such effect has been demonstrated. 

Lindh U, Danersund A, Lindvall A. 1996. Selenium protection against toxicity from cadmium and mercury studied at the cellular level. Cell Mol Biol 42(l) 39-48. 

Lindh U and Johansson E (1987) Protective effects of selenium against mercury toxicity as studied in the rat liver and kidney by nuclear analytical techniques. 

Interactions Overabundance of one trace element can interfere with the metabolic use of another element available at normal levels. For example, addition of large amounts of zinc to a diet interferes with (antagonizes) intestinal copper absorption, resulting in copper deficiency from a diet with adequate copper content. Copper deficiency can provoke iron deficiency and anaemia. Molybdenum deficiency in animals can be induced by co-administration of large amounts of the similar element tungsten. Iron deficiency can also increase retention of cadmium and lead, and selenium has been proposed to protect against cadmium and mercury toxicity. 

MagosL. 1991. Overview on the protection given by selenium against mercurials. Prov Rochester Int Conf Environ Toxic 2 Adv Mercury Toxicol., 289-298. 

The interaction of selenium and methylmercury in the brain appears to be very complex. Despite the clear protective effect of selenite on methylmercury toxicity, selenium increases the mercury content of brain (Prohaska and Ganther, 1977 Chen et al, 1975a). Methylmercury tends to cause a shift in the concentration of selenium from the cytosol to the mitochondrial fraction in the brain. Gel filtration of the brain cytosol, however, revealed that mercury followed a pattern more closely related to protein than to selenium (Prohaska and Ganther, 1977). Therefore, the mechanism of the protective effect of selenium against methylmercury toxicity is still a subject for speculation. 

Various proposals have been presented to explain the interaction of selenium with heavy metals. However, no single one appears to explain the mechanism of interaction with all heavy metals. It appears that there are several mechanisms involved in this interaction and that more than one could be involved with a particular metal. It is clear that selenium does not protect animals against heavy metal toxicity by increasing their excretion instead, it causes an increased retention of metals (Parizek et al, 1971 Wagner et al., 1975 Diplock, 1976 Ganther, 1978 Whanger, 1981). A summary of the proposed interactions of selenium with cadmium, mercury, and silver is presented in Fig. 1. 

Welsh, S. O., and Soares, J. H., 1976, The protective effect of vitamin E and selenium against methyl mercury toxicity in the Japanese quail, Nutr. Rep. Int. 13 43. 

Samples such as hair, nails, blood, urine, and various tissues are analyzed by NAA for both essential and toxic trace elements (Bhandari et al. 1987, Lai et al. 1987). The analysis can be related to determine their effect on disease outcomes. These authors have reported that the diet and environment contribute largely towards the trace elements in the human body. It is has been demonstrated in other works that the selenium concentration in human nails is an accurate monitor of the dietary intake of selenium. As a consequence, the nail monitor has been extensively used to study the protective effect of dietary selenium against cancer and heart disease in numerous prospective case-control studies. In another study by Kanabrocki et al. (1979) on human thumbnails in USA, using thermal NAA technique, the average concentration of metals studied in clinically symptom-free adult female and male subjects were found to be zinc, 184 vs. 153 ppm chromium, 6.8 vs. 4.2 selenium, 0.9 vs. 0.6 gold, 2.6 vs. 0.4 mercury, 1.9 vs. 0.4 silver 0.7 vs. 0.3 cobalt, 0.07 vs. 0.04. In another study, the fluorine concentration in bone biopsy samples was... 

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