Article

Effects of methylmercury exposure on glutathione metabolism, oxidative stress, and chromosomal damage in captive-reared common loon (Gavia immer) chicks

U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, WI 54603, USA.
Environmental Pollution (Impact Factor: 3.73). 12/2008; 156(3):732-8. DOI: 10.1016/j.envpol.2008.06.009
Source: PubMed

ABSTRACT We quantified the level of dietary mercury (Hg), delivered as methylmercury chloride (CH3HgCl), associated with negative effects on organ and plasma biochemistries related to glutathione (GSH) metabolism and oxidative stress, and chromosomal damage in captive-reared common loon (Gavia immer) chicks reared from hatch to 105 days. Mercury-associated effects related to oxidative stress and altered glutathione metabolism occurred at 1.2 microg Hg/g and 0.4 microg Hg/g, an ecologically relevant dietary mercury level, but not at 0.08 microg Hg/g. Among the variables that contributed most to dissimilarities in tissue chemistries between control and treatment groups were increased levels of oxidized glutathione (GSSG), GSH peroxidase, and the ratio of GSSG to GSH in brain tissue; increased levels of hepatic GSH; and decreased levels of hepatic glucose-6-phosphate dehydrogenase (G-6-PDH). Our results also suggest that chronic exposure to environmentally relevant dietary Hg levels did not result in statistically significant somatic chromosomal damage in common loon chicks.

0 Bookmarks
 · 
77 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mercury is a highly toxic metal which induces oxidative stress in the body. The present study aimed to investigate the possible protective effect of neem (Azadirachta indica) leaves extract (NLE) as an antioxidant to protect against mercury-induced oxidative stress and hepatotoxicity. Fourty male albino Sprague Dawley rats were classified into four groups, Control group received distilled water. Mercury-treated group was administrated 2 mg/ Kg b.wt., mercuric chloride (HgCl 2). Mercury and NLE-treated group was treated with 200 mg/Kg b.wt of NLE simultaneously with the same dose of HgCl 2 . NLE-treated group was given NLE only with the same dose. The daily treatments were administered orally for 30 days. Hepatotoxicity was assessed by increased tissue malondialdehyde (MDA), nitric oxide (NO) concentrations, glutathione peroxidase (GPx) activity, serum total bilirubin, direct bilirubin concentrations, serum activities of alanine aminotransferase (ALT), aspartate aminotransferase; (AST), and alkaline phosphatase (ALP) enzymes and decreased hepatic content of reduced glutathione (GSH), vitamin C, vitamin E and serum albumin concentration. Moreover, the histopathological changes revealed destruction of the normal hepatic architecture and severe pathological alterations post HgCl 2 treatment. Carbohydrates, DNA and proteins contents were decreased in the liver tissue. The ultrastructural alterations were represented by degenerative features which covered all the hepatic cells and their cytoplasm contained extensive necrotic areas. Many lipid droplets dispersed within the hepatic cells in addition to the disintegration of most cellular contents. On the other hand, treatment of rats with NLE reversed all these biochemical indices, histopathological, histochemical and ultrastructural alterations. The levels of various serum and tissue parameters for organ toxicity after neem treatment at the dose of 200 mg/kg.b.wt. remained more or less close to the normal values suggesting no significant adverse effects of NLE. The present results implicate that mercury-induced oxidative damage in hepatic tissues was improved by neem leaves extract, with its antioxidant effects. [Journal of American Science 2010; 6(9):735-751]. (ISSN: 1545-1003).
  • [Show abstract] [Hide abstract]
    ABSTRACT: This review summarizes our current state of knowledge regarding the potential biological effects of mercury (Hg) exposure on fish and wildlife in the Canadian Arctic. Although Hg in most freshwater fish from northern Canada was not sufficiently elevated to be of concern, a few lakes in the Northwest Territories and Nunavut contained fish of certain species (e.g. northern pike, Arctic char) whose muscle Hg concentrations exceeded an estimated threshold range (0.5-1.0μgg(-1) wet weight) within which adverse biological effects begin to occur. Marine fish species generally had substantially lower Hg concentrations than freshwater fish; but the Greenland shark, a long-lived predatory species, had mean muscle Hg concentrations exceeding the threshold range for possible effects on health or reproduction. An examination of recent egg Hg concentrations for marine birds from the Canadian Arctic indicated that mean Hg concentration in ivory gulls from Seymour Island fell within the threshold range associated with adverse effects on reproduction in birds. Mercury concentrations in brain tissue of beluga whales and polar bears were generally lower than levels associated with neurotoxicity in mammals, but were sometimes high enough to cause subtle neurochemical changes that can precede overt neurotoxicity. Harbour seals from western Hudson Bay had elevated mean liver Hg concentrations along with comparatively high muscle Hg concentrations indicating potential health effects from methylmercury (MeHg) exposure on this subpopulation. Because current information is generally insufficient to determine with confidence whether Hg exposure is impacting the health of specific fish or wildlife populations in the Canadian Arctic, biological effects studies should comprise a major focus of future Hg research in the Canadian Arctic. Additionally, studies on cellular interactions between Hg and selenium (Se) are required to better account for potential protective effects of Se on Hg toxicity, especially in large predatory Arctic fish, birds, and mammals.
    Science of The Total Environment 06/2014; DOI:10.1016/j.scitotenv.2014.05.142 · 3.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mercury (Hg) is a widespread contaminant that has been shown to induce a wide range of adverse health effects in birds including reproductive, physiological and neurological impairments. Here we explored the relationship between blood total Hg concentrations ([THg]) and oxidative stress gene induction in the aquatic piscivorous Double-crested Cormorants (Phalacrocorax auritus) using a non-lethal technique, i.e., blood gene expression analysis. P. auritus blood was sampled at five sites across the Great Lakes basin, Ontario, Canada and was analyzed for [THg]. To assess cellular stress, the expression of glutathione peroxidases 1 and 3 (GPX1, GPX3), superoxide dismutase 1 (SOD1), heat-shock protein 70 kd-8 (HSP70-8) and glutathione S-transferase µ3 (GSTM3) were measured in whole blood samples using real-time RT-PCR. Results showed a significantly positive correlation between female blood [THg] and both GPX3 and GSTM3 expression. Different levels of oxidative stress experienced by males and females during the breeding season may be influencing the differential oxidative stress responses to blood [THg] observed in this study. Overall, these results suggest that Hg may lead to oxidative stress as some of the cellular stress-related genes were altered in the blood of female P. auritus and that blood gene expression analysis is a successful approach to assess bird health condition.
    Ecotoxicology 05/2014; 23(6). DOI:10.1007/s10646-014-1243-5 · 2.50 Impact Factor

Full-text

Download
85 Downloads
Available from
May 31, 2014