Laboratório de Mamíferos Aquáticos e Bioindicadores Profa Izabel Gurgel, MAQUA, Faculdade de Oceanografia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil.
PLoS One. 2012;7(7):e42162. doi: 10.1371/journal.pone.0042162. Epub 2012 Jul 31.
Top marine predators present high mercury concentrations in their tissues as consequence of biomagnification of the most toxic form of this metal, methylmercury (MeHg). The present study concerns mercury accumulation by Guiana dolphins (Sotalia guianensis), highlighting the selenium-mediated methylmercury detoxification process. Liver samples from 19 dolphins incidentally captured within Guanabara Bay (Rio de Janeiro State, Brazil) from 1994 to 2006 were analyzed for total mercury (THg), methylmercury (MeHg), total organic mercury (TOrgHg) and selenium (Se). X-ray microanalyses were also performed. The specimens, including from fetuses to 30-year-old dolphins, comprising 8 females and 11 males, presented high THg (0.53-132 µg/g wet wt.) and Se concentrations (0.17-74.8 µg/g wet wt.). Correlations between THg, MeHg, TOrgHg and Se were verified with age (p<0.05), as well as a high and positive correlation was observed between molar concentrations of Hg and Se (p<0.05). Negative correlations were observed between THg and the percentage of MeHg contribution to THg (p<0.05), which represents a consequence of the selenium-mediated methylmercury detoxification process. Accumulation of Se-Hg amorphous crystals in Kupffer Cells was demonstrated through ultra-structural analysis, which shows that Guiana dolphin is capable of carrying out the demethylation process via mercury selenide formation.
海洋顶级掠食者体内的组织会积累高浓度的汞，这是由于汞的最具毒性形态——甲基汞（MeHg）在生物体内的生物放大作用。本研究关注的是瓜纳巴拉湾（巴西里约热内卢州）偶然捕获的 19 只瓜纳巴拉海豚（Sotalia guianensis）体内的汞积累情况，重点研究了硒介导的甲基汞解毒过程。1994 年至 2006 年间，从该湾捕获的 19 只海豚（包括胎儿至 30 岁的个体）的肝脏样本，用于分析总汞（THg）、甲基汞（MeHg）、总有机汞（TOrgHg）和硒（Se）的含量。还进行了 X 射线微分析。这些样本包括 8 只雌性和 11 只雄性海豚，年龄从胎儿到 30 岁不等，其 THg（0.53-132 µg/g 湿重）和 Se 浓度（0.17-74.8 µg/g 湿重）均较高。THg、MeHg、TOrgHg 和 Se 与年龄之间存在相关性（p<0.05），同时还观察到 Hg 和 Se 的摩尔浓度之间存在高度正相关（p<0.05）。THg 与 MeHg 对 THg 的贡献百分比之间存在负相关（p<0.05），这是硒介导的甲基汞解毒过程的结果。超微结构分析表明，Kupffer 细胞中积累了硒-汞非晶态晶体，这表明瓜纳巴拉海豚能够通过形成汞硒化物来进行脱甲基化过程。
