Mercury xenobiotics

Xenobiotics that show small U/2 values (i.e., short half-lives) are those that are cleared rapidly from the body, whereas those with high values (i.e., long half-lives) are cleared more slowly and in some cases may accumulate in the body. Insecticides of the DDT family and heavy metals like lead, cadmium, and mercury all display long half-lives, whereas aspirin is a drug that exhibits a short half-life. 

Dutczak WJ, Clarkson TW, Ballatori N. 1991. Biliary-hepatic recycling of a xenobiotic gallbladder absorption of methyl mercury. Am J Physiol 260(6) G873-G880. 

There are virtually no sources of drinking water on Earth that are not contaminated with xenobiotics. Rain water cleanses the atmosphere as it forms and falls. As a result, it contains dissolved acids, organic compounds, and heavy metals such as mercury and selenium in many areas. Surface collection basins from which potable water is drawn—rivers, streams, and lakes—accumulate ground level pollutants in addition to those carried in rain water. Underground water, which is somewhat filtered and generally contains lesser quantities of pollutants than surface water, may itself be contaminated by ground releases of toxicants and by contaminants produced by chemical reactions in the soil and water. 

A wide variety of interactions of selenium with essential and nonessential elements, vitamins, xenobiotics, and sulfur-containing amino acids have been demonstrated in numerous studies. Selenium has been reported to reduce the toxicity of many metals including mercury, cadmium, lead, silver, and to some extent, copper (Frost 1972). Most forms of selenium and arsenic interact to reduce the toxicity of both elements (Levander 1977). Because of selenium s role in the antioxidant glutathione peroxidase enzymes, selenium also reduces the toxicity of metals in vitamin E-deficient animals (Diplock et al. 1967). 

In addition, analysis of hormone levels in serum samples of white sucker Catostomus commersoni) in Lake Superior have been used to complement measurements of physiological response significant differences in the levels of testosterone and estradiol in females, and of testosterone levels in males have been associated with pollution by bleachery effluents (Munkittrick et al. 1991). It has been observed that feral fish captured from areas exposed to established contamination by PAHs, PCBs, and mercury did not exhibit the increased levels of hydrocortisone normally resulting from capture (Hontela et al. 1992). These results were interpreted as showing the adverse effect on sterol metabolism in fish chronically exposed to such pollutants. Collectively, such data draw attention to the subtler effects of exposure to xenobiotics. 

Pollard KM, Lee DK, Casiano CA, Bluthner M, Johnston MM, Tan EM. The autoimmunity-inducing xenobiotic mercury interacts with the autoantigen fibrillarin and modifies its molecular and antigenic properties. J Immunol 1997 158 3521-3528. Kubicka-Muranyi M, Kremer J, Rottmann N, Lubben B, Albers R, Bloksma N, Luhrmann R, Gleichmann E. Murine systemic autoimmune disease induced by mercuric chloride T helper cells reacting to self proteins. Int Arch Allergy Immunol 1996 109 11-20. 

Neff JM, Cox BA, Dixit D, Anderson JW (1976) Accumulation and release of petroleum-derived aromatic hydrocarbons by four species of marine animals. Mar Biol 38 279-289 Nelson A, Auffret N (1988) Interaction of xenobiotics with mercury-adsorbed phospholipid mono-layers. Mar Env Res 24 51-56... 

The amount of time that a chemical remains in the body is measured as the biological half-life—also known as the half-life of elimination, and designated as T1/2. This is the amount of time it takes for half of the concentration to be eliminated from the body. For compounds that are quickly metabolized and eliminated, this biological half-life is short—a matter of hours or days. For example, proteins in your body s liver have a biological half-life of around 10 days. Many reactive xenobiotics have half-lives of only a few hours. Metallic mercury is a chronic poison in low, continuous doses and has a half-life of 20-90 days. Compounds such as the chlorinated hydrocarbons can be stored for long periods of time, often for years. 

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