Biological Trace Element Research

, Volume 119, Issue 3, pp 255–268 | Cite as

Importance of Molar Ratios in Selenium-Dependent Protection Against Methylmercury Toxicity

  • Nicholas V. C. RalstonEmail author
  • J. Lloyd BlackwellIII
  • Laura J. Raymond


The influence of dietary selenium (Se) on mercury (Hg) toxicity was studied in weanling male Long Evans rats. Rats were fed AIN-93G-based low-Se torula yeast diets or diets augmented with sodium selenite to attain adequate- or rich-Se levels (0.1, 1.0 or 15 μmol/kg, respectively) These diets were prepared with no added methylmercury (MeHg) or with moderate- or high-MeHg (0.2, 10 or 60 μmol/kg, respectively). Health and weights were monitored weekly. By the end of the 9-week study, MeHg toxicity had impaired growth of rats fed high-MeHg, low-Se diets by approximately 24% (p < 0.05) compared to the controls. Growth of rats fed high-MeHg, adequate-Se diets was impaired by approximately 8% (p < 0.05) relative to their control group, but rats fed high-MeHg, rich-Se diets did not show any growth impairment. Low-MeHg exposure did not affect rat growth at any dietary Se level. Concentrations of Hg in hair and blood reflected dietary MeHg exposure, but Hg toxicity was more directly related to the Hg to Se ratios. Results support the hypothesis that Hg-dependent sequestration of Se is a primary mechanism of Hg toxicity. Therefore, Hg to Se molar ratios provide a more reliable and comprehensive criteria for evaluating risks associated with MeHg exposure.


Selenium Mercury Methylmercury Toxicity Brain Blood 


Acknowledgment and Disclaimer

The research described in this article has been funded by the U.S. Environmental Protection Agency through Grant CR830929-01 to the University of North Dakota Energy and Environmental Research Center. This article has not been subjected to the Agency’s peer and policy review and, therefore, does not necessarily reflect the views of the Agency, and no official endorsement should be inferred.


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Copyright information

© Humana Press Inc. 2007

Authors and Affiliations

  • Nicholas V. C. Ralston
    • 1
    Email author
  • J. Lloyd BlackwellIII
    • 2
  • Laura J. Raymond
    • 1
  1. 1.Energy and Environmental Research CenterUniversity of North DakotaGrand ForksUSA
  2. 2.Department of EconomicsUniversity of North DakotaGrand ForksUSA

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