Interactions between methylmercury and selenomethionine injected into mallard eggs

Abstract

Methylmercury chloride and seleno-L-methionine were injected separately or in combinations into mallard eggs (Anas platyrhynchos), and embryo mortality and teratogenic effects (deformities) were modeled using a logistic regression model. Methylmercury was injected at doses that resulted in concentrations of 0, 0.2, 0.4, 0.8, and 1.6 µg/g Hg in the egg on a wet weight basis and selenomethionine at doses that resulted in concentrations of 0, 0.1, 0.2, 0.4, and 0.6 µg/g Se in the egg, also on a wet weight basis. When selenomethionine and methylmercury were injected separately, hatching probability decreased in both cases. However, when methylmercury was injected at 1.6 µg/g in combination with selenomethionine at 0.2 µg/g, the presence of the methylmercury resulted in less embryo mortality than had been seen with 0.2 µg/g Se by itself, but it increased the number of deformed embryos and hatchlings. Selenomethionine appeared to be more embryotoxic than equivalent doses of methylmercury when injected into eggs, and both injected methylmercury and selenomethionine were more toxic to mallard embryos than when deposited naturally in the egg by the mother. The underlying mechanisms behind the interactions between methylmercury and selenomethionine and why methylmercury appeared to improve hatching probability of Se-dosed eggs yet increased deformities when the two compounds were combined are unclear. These findings warrant further studies to understand these mechanisms in both laboratory and field settings.

Selenium and mercury molar ratios in saltwater fish from New Jersey: Individual and species variability complicate use in human health fish consumption advisories

“…It has long been known that selenium confers some protection against mercury toxicity in some organisms, but it is less well appreciated that mercury may likewise reduce selenium toxicity (Klimstra et al 2011). While data is accumulating on selenium:mercury ratios there is no consensus as to how much selenium is needed to reduce the risk of mercury toxicity, nor is it clear whether there is a linear relationship between the hypothesized protective ratio and mercury levels.…”

“…Since selenoenzymes play an important role in anti-oxidant defenses, this interaction may explain the oxidative damage attributable to methylmercury (Beyrouty and Chan, 2006; Cabanero et al, 2007; Stringari et al, 2008; Pinheiro et al, 2009; Ralston, 2009; Ralston and Raymond, 2010). Both the toxicokinetics and toxicodynamics of the selenium and mercury interaction require further extensive study, as the effects differ depending on the forms or species of selenium and of mercury (Dang and Wang, 2011) and how they are administered (Klimstra et al, 2011). Identification and refinement of the protective effect of selenium on mercury toxicity is an important contribution that is needed to interpret molar ratio data.…”

“…Identification and refinement of the protective effect of selenium on mercury toxicity is an important contribution that is needed to interpret molar ratio data. There is at least a theoretic limit to the protection conferred by selenium since it is highly toxic by itself (Klimstra et al 2011). …”

Mercury in birds of San Francisco Bay-Delta, California: trophic pathways, bioaccumulation, and ecotoxicological risk to avian reproduction

“…During the shorebird-breeding period, the diet of avocets and stilts consisted of predominately seasonally abundant Corixidae (see above); thus, Corixidae might be an invertebrate taxa of particular concern regarding trophic transfer of total mercury. 42 …”

Selenium and mercury molar ratios in commercial fish from New Jersey and Illinois: Variation within species and relevance to risk communication

“…Selenoenzymes play an important role in antioxidant defenses, which may explain the oxidative damage attributable to methylmercury (Cabanero et al, 2007; Pinheiro et al, 2009; Ralston and Raymond, 2010). The toxicokinetics and toxicodynamics of the selenium and mercury interactions require extensive study as effects differ depending on the forms or species of selenium and of mercury (Dang and Wang, 2011; Khan and Wang, 2009), administration methods (Klimstra et al, 2011), and relationship among them (Falnoga et al, 2006; Farina et al, 2011). There is a limit to the protection of selenium on mercury toxicity, and selenium itself can be highly toxic (Klimstra et al, 2011).…”