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首页> 外文期刊>Environmental Science & Technology >Biodynamics, Subcellular Partitioning, And Ultrastructural Effects Of Organic Selenium In A Freshwater Bivalve
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Biodynamics, Subcellular Partitioning, And Ultrastructural Effects Of Organic Selenium In A Freshwater Bivalve

机译：淡水双壳类动物体内有机硒的生物力学，亚细胞分配和超微结构影响

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Selenium is a trace element characterized by concentrations that narrowly range between being essential and being toxic. Even though inorganic selenite and selenate are the predominant chemical forms of Se in surface waters, the toxicity of Se to aquatic organisms is mostly governed by the bioavailability of organic selenium within food webs. The present study was designed to evaluate organic selenium bioaccumulation and toxicity patterns in the freshwater sentinel species Corbicula fluminea. Waterborne selenomethionine (SeMet) exposure was used to mimic dietary organo-Se uptake. Our results demonstrate that SeMet is accumulated to a relatively high extent with a concentration factor of 770 (wet weight basis). Higher uptake than depuration rates suggest that bivalves deal with high Se amounts using a strategy of detoxification based on Se sequestration that could involve granules, as shown by a strong increase of Se in the paniculate subcellular fraction. Selenium is persistent in the cytosol of bivalves exposed to SeMet where it is found in proteins of a wide range of molecular mass, indicating a possible replacement of methionine by selenomethionine. A subsequent alteration of protein function might be one of the mechanisms of Se toxicity that could explain the histopathological effects we observed in gills by using transmission electronic microscopy. Those analyses showed changes in gill filament ultrastructure and suggested mitochondria asthe first target for SeMet cytotoxicity, with alterations of the outer membrane and of cristae morphology. Organo-Se would thus not only be toxic via indirect mechanisms of maternal transfer as it was suggested for fish but also directly. Our results on Se distribution agree with studies that used dietary Se transfer, and highlight the relevance (and less expensive way) of using SeMet water-only exposure protocols to mimic the real environment.
机译：硒是一种微量元素，其特征在于浓度范围介于必需和有毒之间。尽管无机亚硒酸盐和硒酸盐是地表水中硒的主要化学形式，但是硒对水生生物的毒性主要取决于食物网中有机硒的生物利用度。本研究旨在评估淡水前哨物种Corbicula fluminea中有机硒的生物富集和毒性模式。水性硒代蛋氨酸（SeMet）暴露用于模拟饮食中有机硒的摄入。我们的结果表明，SeMet以770（湿重）的浓缩因子相对较高地积累。高于净化率的摄取表明，双壳类动物使用基于Se螯合的解毒策略来处理高Se含量，该策略可能涉及颗粒，如圆锥形亚细胞部分中Se的强烈增加所表明。硒在暴露于SeMet的双壳类动物的细胞质中具有持久性，在多种分子量的蛋白质中都存在硒，这表明硒代蛋氨酸可能替代蛋氨酸。随后蛋白质功能的改变可能是Se毒性的机制之一，可以解释我们通过使用透射电子显微镜在g中观察到的组织病理学效应。这些分析表明g丝超微结构的变化，并提示线粒体是SeMet细胞毒性的第一个靶标，其外膜和ista的形态发生了改变。因此，有机硒不仅会通过暗示的鱼类母体转移的间接机制产生毒性，而且还会直接产生毒性。我们关于硒分布的研究结果与使用膳食硒转移的研究相吻合，并强调了使用SeMet纯水暴露方案模拟真实环境的相关性（且价格较低）。

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