Mercury liver

Pokras, M.A., C. Hanley, and Z. Gordon. 1998. Liver mercury and methylmercury concentrations in New England common loons (Gavia immer). Environ. Toxicol. Chem. 17 202-204. 

Metals are generally circulated bound to some blood protein and can selectively bioaccumulate thus, metals can affect either specific target organs or multiple anatomical sites. For example, lead can deposit in the bone, affect the central nervous system (CNS), and interfere with the metabolism of the heme in hemoglobin cadmium appears to concentrate in the kidneys and the liver, mercury is a CNS toxin. 

Massie HR, Greco ME, Vadlamudi L. 1993. The brain-to-liver mercury ratio increases with aging in mice. Exper Gerontol 28(2) 161-167. 

Iodine occurs to a minute extent (less than 0.001 %) in sea water, but is found in greater concentration, combined in organic form, in certain seaweeds, in oysters and in cod livers. Crude Chile saltpetre, or caliche contains small amounts of sodium iodate, NalOj. from which iodine can be obtained (see below). Some insoluble iodides, for example liiose of silver and mercury(II), occur in Mexico. Iodine is found in the human body in the compound thyroxin in the thyroid gland deficiency of iodine in diet causes enlargement of this gland (goitre). 

The hazards of chemicals are commonly detected in the workplace first, because exposure levels there are higher than in the general environment. In addition, the exposed population is well known, which allows early detection of the association between deleterious health effects and the exposure. The toxic effects of some chemicals, such as mercury compounds and soot, have been known already for centuries. Already at the end of the eighteenth century, small boys who were employed to climb up the inside of chimneys to clean them suffered from a cancer of the scrotum due to exposure to soot. This was the first occupational cancer ever identified. In the viscose industry, exposure to carbon disulfide was already known to cause psychoses among exposed workers during the nineteenth century. As late as the 1970s, vinyl chloride was found to induce angiosarcoma of the liver, a tumor that was practically unknown in ocher instances. ... 

FIGURE 8.4 Mercury residues in the livers of Swedish birds (from Walker 1975). 

Metallothioneins are a group of small proteins (about 6.5 kDa), found in the cytosol of cells, particularly of liver, kidney, and intestine. They have a high content of cysteine and can bind copper, zinc, cadmium, and mercury. The SH groups of cysteine are involved in binding the metals. Acute intake (eg, by injection) of copper and of certain other metals increases the amount (induction) of these proteins in tissues, as does administration of certain hormones or cytokines. These proteins may function to store the above metals in a nontoxic form and are involved in their overall metaboHsm in the body. Sequestration of copper also diminishes the amount of this metal available to generate free radicals. 

A knowledge of physiology and pharmacokinetics is needed (Fanis et al. 1993 Monteiro and Furness 2001). Levels of mercuiy normally vary among internal tissues, and the time to equilibrate within each tissue varies. For example, blood mercury levels normally reflect veiy recent exposure, while brain and liver levels reflect longer-term exposure. Tissue-specific mechanisms of detoxification and seqnestration, among other processes, must be understood to define the bioactive moiety in observed tissue bmdens before a clear expression of toxicity can be derived (Woodetal. 1997). 

Liver is 1 of the tissues most frequently analyzed for contaminant residne in wildlife, but maybe 1 of the least useful because of the poor correlation between fiver mercniy concentration and effects, and because of the tendency of the liver to accumulate mercury over time (Stewart et al. 1999 Scheuhammer et al. 2001). Liver is a major site of demethylation therefore, the proportion of fiver mercury present as MeHg is not representative of exposure to MeHg. Moreover, most mercury in fiver is botmd to metallothionein or other suUydryl-bearing proteins, which immobilize it (Med-insky and Klaassen 1996 Yasutake etal. 1997 Aschner 1999). Therefore, fiver mercury residue values must be used with caution, and only when more suitable tissues are unavailable. 

Sundlof SF, Spaulding MG, Wentworth JD, Steible CK. 1994. Mercury in livers of wading birds (Ciconiiformes) in Southern Florida. Arch Environ Contam Toxicol 27 299-305. 

Wagemann RE, Trebacz G, Boila G, Lockhhart WL. 2000. Mercury species in the liver of ringed seals. Sci Total Environ 261 21-32. 

Weech SA, Wilson LK, Langelier KM, Elliott JE. 2003. Mercury residues in livers of bald eagles Haliaeetus leucocephalus) found dead or dying in British Columbia, Canada (1987-1994). Arch Environ Contam Toxicol 45 562-569. 

Vermilion and cinnabar are two bright red, toxic minerals that share an identical composition (they are both composed of mercury sulfide) but have different crystal structures. Two kinds of vermilion are known one of natural origin and another made artificially. Finely ground natural vermilion may vary in hue from red to liver-brown and even to black. Artificial vermilion was made from mercury and sulfur the method of preparation seems to have been developed by the Chinese and was introduced into Europe only during the eighth century c.e. (Gettens et al. 1972). 

Evidence suggests that lead exacerbates the toxic effects of mercury. In the rat, the administration of lead nitrate increased kidney and liver glutathione content and resulted in increased mercury deposition in the kidney, along with increased lethality in rats (Congiu et al. 1979). 

Penicillamine is reported to be more than 80% bound to plasma protein. The compound is metabolized in the liver. N-acetylpenicillamine is more effective than penicillamine in protecting against the toxic effect of mercury, presumably because it is even more resistant to metabolism [7,2]. 

In this regard, high liver/muscle ratios of mercury concentration were reported in fish exposed to the effluents from a chlor-alkali plant in a contaminated area [68, 69]. Then, liver of fish downstream from the plant also had very high inorganic mercury to THg ratios [69]. 

Raldua D, Diez S, Bayona JM, Barcelo D (2007) Mercury levels and liver pathology in feral fish living in the vicinity of amercury cell chlor-alkali factory. Chemosphere 66 1217-1225... 

A battery of different biochemical quantitative assays was applied to many different tissues and species. DNA damage and lipid peroxidation assays measure the direct impact of genotoxics and oxidant pollutants [16,17] whereas alteration of GSH levels in liver is a marker for oxidative stress [18]. Mercury and other heavy metals are known to induce metallothionein levels in different tissues although this effect is variable in different species and organs [19-22]. 

GSH, GSSG quantitation Cc, Dp, Pc Liver (Cc), digestive gland (Dp, Pc) Oxidative stress, mercury poisoning... 

This area was the most profusely studied in the AQUATERRA project in terms of biological effects in fish populations. Barbel and bleak were the sentinel species selected in this area and an array of histological and biochemical tests were used to monitor the impact due to three major sources of pollution mercury and OCs at Monzon (with a comparison in one of the papers with Flix) and PBDEs in Barbastro [1—4, 37]. Mercury pollution was directly correlated to an increase of MTprotein in the liver of barbel captured downstream Monzon when compared to samples captured upstream (Fig. 3a). However, mRNA quantitative analyses failed to show any differences between downstream and upstream Monzon, neither correlated with MT protein levels. Further studies showed that MT mRNA in liver is a rather weak marker for chronic metal pollution in liver (see below) [4], The presence of degenerative hepatocytes in barbels and bleaks was also linked to mercury poisoning although it can also reflect the impact by other pollutants, like OCs or PBDEs (Fig. 3e). 

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