Methylmercury-induced changes in the activities of neurotransmitter enzymes in nervous tissues of the rat

Omata, Saburo; Hirakawa, Eihime; Daimon, Yoshie; Uchiyama, Mariko; Nakashita, Harumi; Horigome, Tsuneyoshi; Sugano, Iku; Sugano, Hiroshi

doi:10.1007/bf00317007

Cited by 21 publications

(13 citation statements)

References 31 publications

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“…27 In vitro studies have shown that, unlike organophosphates, MeHg does not directly inhibit AChE activity in mammals at physiologically relevant concentrations (ie, IC50 !/1 mM). 28,29 However, MeHg is a potent inhibitor of other components within this pathway, including choline acetyltransferase activity (ie, reduced synthesis of acetylcholine), 28,29 and mACh receptor binding (ie, obstruct signal transduction) 30,31 and the net outcome of these interactions is impeded transmission of cholinergic signals. Similar to our findings, others have measured Hg-related decreases in AChE activity, in vivo.…”

Section: Discussionmentioning

confidence: 99%

Cholinesterase and monoamine oxidase activity in relation to mercury levels in the cerebral cortex of wild river otters

et al. 2007

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Mercury (Hg) is a global pollutant that is neurotoxic to many mammalian species. The present study was conducted to determine if the bioaccumulation of Hg by wild river otters ( Lontra canadensis) could be related to variations in the activities of key neurochemical enzymes. River otters were collected from Ontario and Nova Scotia (Canada) during the trapping seasons, spanning 2002-2004, and their brains were dissected into the cerebral cortex and cerebellum. The activities of cholinesterase (ChE) and monoamine oxidase (MAO) were measured from each sample and correlated with concentrations of brain Hg from the same animal. Significant negative correlations were found between concentrations of brain Hg and ChE (total Hg: r= -0.42; MeHg: r= -0.33) and MAO (total Hg: r= -0.31; MeHg: r= -0.42) activity in the cerebral cortex. The scatterplots relating concentrations of brain Hg and enzyme activity in the cerebral cortex were wedge-shaped, and could be fitted with quantile regression modeling, suggesting that Hg may act as a limiting factor for ChE and MAO activity. No relationships were found in the cerebellum. These data suggest that environmentally relevant concentrations of Hg may influence the activities of ChE and MAO in the cerebral cortex of river otters, and by extension, other fish-eating mammals.

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Section: Discussionmentioning

confidence: 99%

Cholinesterase and monoamine oxidase activity in relation to mercury levels in the cerebral cortex of wild river otters

et al. 2007

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“…For example, laboratory rats [47] and mice [48] exposed to MeHg had decreased concentrations of brain acetylcholine, the primary agonist of the mACh receptor. Reduced acetylcholine levels, as a result of MeHg exposure, are supported by mechanistic studies demonstrating that MeHg can suppress the activity of choline acetyltransferase [25,26], inhibit the voltage‐gated entry of acetylcholine into pre‐ and postsynaptic nerve endings [49,50], and impair the binding of [ 3 H]‐QNB to the mACh receptor [31]. Because Hg may reduce the cellular pool of acetylcholine, up‐regulation of the mACh receptor in Hg‐exposed mink (Figs.…”

Section: Discussionmentioning

confidence: 99%

Effects of mercury on neurochemical receptor‐binding characteristics in wild mink

Basu

Klenavic

Gamberg³

et al. 2005

Enviro Toxic and Chemistry

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Piscivorous wildlife, such as mink (Mustela vison), routinely are exposed to mercury (Hg) in their natural environment at levels that may cause adverse behavioral outcomes. The purpose of this study was to determine if a correlation exists between neurochemical receptors and concentrations of Hg in the brains of wild mink. Specifically, receptor-binding assays were conducted to characterize the muscarinic cholinergic (mACh) and dopaminergic-2 (D2) systems in brain tissues collected from mink trapped in the Yukon Territory, Ontario, and Nova Scotia (Canada), and values were correlated with total Hg and methyl Hg (MeHg) concentrations in the brains. A significant correlation was found between Hg (total Hg and MeHg) and mACh receptor density (r = 0.546; r = 0.596, respectively) or ligand affinity (r = 0.413; r = 0.474, respectively). A significant negative correlation was found between total Hg and D2 receptor density (r = -0.340) or ligand affinity (r = -0.346). These correlations suggest that environmentally relevant concentrations of Hg may alter neurochemical function in wild mink, and that neurochemical receptor-binding characteristics can be used as a novel biomarker to assess Hg's effects on wildlife. Given the importance of the muscarinic cholinergic and dopaminergic pathways in animal behavior, further studies are required to explore the physiological and ecological significance of these findings.

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“…Furthermore, in the sympathetic ganglion of the rat, MMC seems to inhibit the release of acetylcholine from presynaptic nerve terminals (Alkadhi and Taha 1982). The activity of choline acetyltransferase in the brain of rat is also inhibited by MMC (10 mg/kg/day, for 3-15 days) (Omata et al 1982).…”

Section: Discussionmentioning

confidence: 99%

Effects of methylmercuric chloride and bis (methylmercuric) selenide on responses of isolated intestinal smooth muscle of the guinea-pig.

Fukushi

Yamamoto

1985

Tohoku J. Exp. Med.

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The neurologically toxic substance, methylmercury, is detoxicated by simultaneous application of selenite. In vivo formation of bis (methylmercuric) selenide has been suggested as the mechanism of detoxication by selenite. By using isolated guinea-pig taenia coli preparations, the effects of methylmercuric chloride and bis (methylmercuric) selenide on contractile responses to nerve and direct stimulation were investigated. Application of either drugs scarcely affected contractile responses to direct stimulation. However, contractile responses to nerve stimulation were severely reduced by methylmercuric chloride. The effect of bis (methylmercuric) selenide was considerably weaker than methylmercuric chloride. The site blocked by methylmercuric chloride and bis (methylmercuric) selenide in the taenia preparation was discussed methylmercuric chloride (MMC) ; bis ( methylmercuric ) selenide (BMS) ; guinea-pig taenia coli

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Methylmercury-induced changes in the activities of neurotransmitter enzymes in nervous tissues of the rat

Cited by 21 publications

References 31 publications

Cholinesterase and monoamine oxidase activity in relation to mercury levels in the cerebral cortex of wild river otters

Cholinesterase and monoamine oxidase activity in relation to mercury levels in the cerebral cortex of wild river otters

Effects of mercury on neurochemical receptor‐binding characteristics in wild mink

Effects of methylmercuric chloride and bis (methylmercuric) selenide on responses of isolated intestinal smooth muscle of the guinea-pig.

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