Division of Life Science, The Hong Kong University of Science and Technology (HKUST) , Clear Water Bay, Kowloon, Hong Kong, China.
Marine Environmental Laboratory, HKUST Shenzhen Research Institute , Shenzhen 518057, China.
Environ Sci Technol. 2017 Jun 6;51(11):6441-6451. doi: 10.1021/acs.est.7b00923. Epub 2017 May 26.
Mercury (Hg) in fish has attracted public attention for decades, and methylmercury (MeHg) is the predominant form in fish. However, the in vivo MeHg demethylation and its influence on Hg level in fish have not been well-addressed. The present study investigated the in vivo demethylation process in a marine fish (black seabream, Acanthopagrus schlegeli) under dietary MeHg exposure and depuration and quantified the biotransformation and interorgan transportation of MeHg by developing a physiologically based pharmacokinetic (PBPK) model. After exposure, we observed a 2-fold increase of the whole-body inorganic Hg (IHg), indicating the existence of an in vivo demethylation process. The results strongly suggested that the intestine played a predominant role in MeHg demethylation with a significant rate (6.6 ± 1.7 day) during exposure, whereas the hepatic demethylation appeared to be an extremely slow (0.011 ± 0.001 day) process and could hardly affect the whole-fish Hg level. Moreover, demethylation in the intestine served as an important pathway for MeHg detoxification. Our study also pointed out that in vivo MeHg demethylation could influence Hg level and speciation in fish although food is the major pathway for Hg accumulation. Enhancing in vivo MeHg biotransformation (especially in the intestine) could be a potential key solution in minimizing Hg contamination in fish. The related factors involved in intestinal demethylation deserve more attention in the future.
汞（Hg）在鱼类中引起了公众数十年的关注，而甲基汞（MeHg）是鱼类中主要的存在形式。然而，体内 MeHg 的去甲基化及其对鱼类中 Hg 水平的影响尚未得到很好的解决。本研究通过建立生理相关的药代动力学（PBPK）模型，研究了在膳食 MeHg 暴露和清除条件下，海水鱼（黑鲷，Acanthopagrus schlegeli）体内的 MeHg 去甲基化过程，并定量了 MeHg 的生物转化和器官间转运。暴露后，我们观察到全身无机汞（IHg）增加了两倍，表明存在体内去甲基化过程。结果强烈表明，肠道在暴露期间对 MeHg 去甲基化起着主要作用，具有显著的速率（6.6±1.7 天），而肝脏去甲基化似乎是一个极其缓慢的（0.011±0.001 天）过程，几乎不会影响整条鱼的 Hg 水平。此外，肠道中的去甲基化是 MeHg 解毒的重要途径。我们的研究还指出，尽管食物是汞积累的主要途径，但体内 MeHg 去甲基化会影响鱼类的 Hg 水平和形态。增强体内 MeHg 的生物转化（特别是在肠道中）可能是减少鱼类中 Hg 污染的一个潜在关键解决方案。肠道去甲基化涉及的相关因素值得在未来进一步关注。
