Mercury in brain

Lind B, Friberg L, Nylander M. 1988. Preliminary studies on methyhnercury biotransformation and clearance in the brain of primates. II. Demethylation of mercury in brain. J Trace Elem Exp Med 1 49-56. 

Pedersen MB, Hansen JC, Mulvad G, Pedersen HS, Gregersen M and Danscher G (1999) Mercury accumulations in brains from populations exposed to high and low dietary levels of methyl mercury. Concentration, chemical form and distribution of mercury in brain samples from autopsies. Int J Circumpolar Health 58 96-107. 

The mink Mustela vision) is a piscivorous mammal that also has been exposed to relatively high dietary levels of methyl mercury in North America in recent times. In a Canadian study, mink trapped in Yukon territory, Ontario, and Nova Scotia were analyzed for levels of mercury and abundance of muscarinic, cholinergic and dopaminergic receptors in the brain (Basu et al. 2005). A correlation was found between total Hg levels and abundance of muscarinic receptors, but a negative correlation was found between total Hg and abundance of dopaminergic receptors. Thus, it was suggested that environmentally relevant concentrations of Hg (much of it in methyl form) may alter neurochemical function. The highest levels of mercury contamination were found in mink from Nova Scotia that had a mean concentration of total Hg of 5.7 pg/g in brain, 90% of which was methyl mercury. 

Most of the mercury in muscle is present as MeHg. Barr (1986) reported that adult loons from a site closest to a mercury somce with 1.87 ppm Hg in fish, resulted in a muscle Hg concentration of 4.57 ppm ww and a brain Hg concentration of 1.49 ppm. Those loons had only 20% of territories successful (Barr 1986). Mallard hens receiving 0.5 ppm dietary mercury for 18 months had a muscle Hg concentration of 0.82 ppm compared with brain Hg = 0.50 ppm. Mallard hens receiving 3 ppm for the same period had 5.01 ppm in muscle and 4.57 in brain (Heinz 1976). Based on these assessments, muscle Hg concentration is more representative of brain Hg concentration and correlates better with effect than the more commonly measured fiver residue. It is also possible to sample muscle tissue nonlethally via biopsy, in... 

Yang MG, Krawford KS, Gareia JD, Wang JHC, Lei KY. 1972. Deposition of mercury in fetal and maternal brain. Proc Soc Exp Biol Med 141 1004-1007. 

Pavlenko, V. B., Evstafyeva, I. A., Evstafyeva, E. V., Artov, A. M. (2000). Psychological features and parameters of bioelectrical activity of a brain at the teenagers in connection with the content of mercury in organism. Tavricheskiy medico-biologichesky vestnik, 4, 3 4, 121-125. 

Divalent mercury in rats has been reported to poorly penetrate the blood-brain barrier [23], However, there is an impairment of the blood-brain barrier within hours after mercury treatment [24, 25], By means of autoradiographic techniques, it was demonstrated [26] that after a single intravenous injection of labelled mercuric chloride, large portions of the radioactive mercury were detected in the cerebellar grey matter, area postrema, hypothalamus and areas near the lateral ventricle of mice. 

Elemental mercury in the form of mercury vapor is readily and rapidly absorbed into the bloodstream when inhaled and easily crosses the blood-brain barrier and the placenta. Oral ingestion of elemental mercury is far less hazardous than inhalation of mercury vapor due to its poor absorption in the gut. Acute, high level exposure to mercury vapor can result in respiratory, cardiovascular, neurological, and gastrointestinal effects, and even death. 

Warren, H.V., Horksy, S J. and Gould, C.E. (1983) Quantitative analysis of zinc, copper, lead, molybdenum, bismuth, mercury and arsenic in brain and other tissues from multiple sclerosis and non-multiple sclerosis cases. Science of the Total Environment, 29(1-2), 163-69. 

Mercury exists in the environment in three main chemical forms elemental mercury (Hg°), inorganic mercurous (Hg+) and mercuric (Hg2+) salts, and organic methylmer-cury (CH3Hg) and dimethylmercury (CH3HgCH3) compounds. Elemental mercury, in the form of mercury vapor, is almost completely absorbed by the respiratory system, whereas ingested elemental mercury is not readily absorbed and is relatively harmless. Once absorbed, elemental mercury can cross the blood-brain barrier into the nervous system. Most exposure to elemental mercury tends to be from occupational sources. 

C.A. Glomski, H. Brody, and S.K.K. Pillay, Distribution and concentration of mercury in autopsy specimens of human brain. Nature (London) 232 200, 1971. 

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