State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Institute of Environment and Health, Jianghan University, Wuhan 430056, China.
J Environ Sci (China). 2018 Jun;68:143-150. doi: 10.1016/j.jes.2018.02.004. Epub 2018 Feb 16.
Selenium (Se) is commonly recognized as a protective element with an antagonistic effect against mercury (Hg) toxicity. However, the mechanisms of this Hg-Se antagonism are complex and remain controversial. To gain insight into the Hg-Se antagonism, a type of unicellular eukaryotic protozoa (Tetrahymena malaccensis, T. malaccensis) was selected and individually or jointly exposed to two Hg and three Se species. We found that Se species showed different toxic effects on the proliferation of T. malaccensis with the toxicity following the order: selenite (Se(IV))>selenomethionine (SeMeth)>selenate (Se(VI)). The Hg-Se antagonism in Tetrahymena was observed because the joint toxicity significantly decreased under co-exposure to highly toxic dosages of Hg and Se versus individual toxicity. Unlike Se(IV) and Se(VI), non-toxic dosage of SeMeth significantly decreased the Hg toxicity, revealing the influence of the Se species and dosages on the Hg-Se antagonism. Unexpectedly, inorganic divalent Hg (Hg) and monomethylmercury (MeHg) also displayed detoxification towards extremely highly toxic dosages of Se, although their detoxifying efficiency was discrepant. These results suggested mutual Hg-Se detoxification in T. malaccensis, which was highly dependent on the dosages and species of both elements. As compared to other species, SeMeth and MeHg promoted the Hg-Se joint effects to a higher degree. Additionally, the Hg contents decreased for all the Hg-Se co-exposed groups, revealing a sequestering effect of Se towards Hg in T. malaccensis.
硒（Se）通常被认为是一种具有拮抗汞（Hg）毒性作用的保护元素。然而，这种 Hg-Se 拮抗作用的机制很复杂，仍存在争议。为了深入了解 Hg-Se 拮抗作用，选择了一种单细胞真核原生动物（Tetrahymena malaccensis，T. malaccensis），并分别或联合暴露于两种 Hg 和三种 Se 物种。我们发现，Se 物种对 T. malaccensis 的增殖表现出不同的毒性作用，毒性顺序为：亚硒酸盐（Se(IV)）>硒代蛋氨酸（SeMeth）>硒酸盐（Se(VI)）。在 Tetrahymena 中观察到 Hg-Se 拮抗作用，因为在联合暴露于高毒性剂量的 Hg 和 Se 时，联合毒性明显低于单独毒性。与 Se(IV)和 Se(VI)不同，无毒剂量的 SeMeth 显著降低了 Hg 的毒性，表明 Se 物种和剂量对 Hg-Se 拮抗作用的影响。出乎意料的是，无机二价 Hg（Hg）和甲基汞（MeHg）对极高毒性剂量的 Se 也表现出解毒作用，尽管它们的解毒效率不同。这些结果表明在 T. malaccensis 中存在相互的 Hg-Se 解毒作用，这高度依赖于两种元素的剂量和物种。与其他物种相比，SeMeth 和 MeHg 更能促进 Hg-Se 联合作用，达到更高的程度。此外，所有 Hg-Se 共同暴露组的 Hg 含量都降低了，这表明 Se 在 T. malaccensis 中对 Hg 具有螯合作用。
