Day Rusty D, Segars Al L, Arendt Michael D, Lee A Michelle, Peden-Adams Margie M
National Institute of Standards and Technology, Hollings Marine Laboratory, Charleston, South Carolina 29412, USA.
Environ Health Perspect. 2007 Oct;115(10):1421-8. doi: 10.1289/ehp.9918.
Mercury is a pervasive environmental pollutant whose toxic effects have not been studied in sea turtles in spite of their threatened status and evidence of immunosuppression in diseased populations.
In the present study we investigate mercury toxicity in loggerhead sea turtles (Caretta caretta) by examining trends between blood mercury concentrations and various health parameters.
Blood was collected from free-ranging turtles, and correlations between blood mercury concentrations and plasma chemistries, complete blood counts, lysozyme, and lymphocyte proliferation were examined. Lymphocytes were also harvested from free-ranging turtles and exposed in vitro to methylmercury to assess proliferative responses.
Blood mercury concentrations were positively correlated with hematocrit and creatine phosphokinase activity, and negatively correlated with lymphocyte cell counts and aspartate amino-transferase. Ex vivo negative correlations between blood mercury concentrations and B-cell proliferation were observed in 2001 and 2003 under optimal assay conditions. In vitro exposure of peripheral blood leukocytes to methylmercury resulted in suppression of proliferative responses for B cells (0.1 microg/g and 0.35 microg/g) and T cells (0.7 microg/g).
The positive correlation between blood mercury concentration and hematocrit reflects the higher affinity of mercury species for erythrocytes than plasma, and demonstrates the importance of measuring hematocrit when analyzing whole blood for mercury. In vitro immunosuppression occurred at methylmercury concentrations that correspond to approximately 5% of the individuals captured in the wild. This observation and the negative correlation found ex vivo between mercury and lymphocyte numbers and mercury and B-cell proliferative responses suggests that subtle negative impacts of mercury on sea turtle immune function are possible at concentrations observed in the wild.
汞是一种普遍存在的环境污染物，尽管海龟处于濒危状态且有证据表明患病群体存在免疫抑制，但尚未对其毒性作用进行研究。
在本研究中，我们通过检查血液汞浓度与各种健康参数之间的趋势，来研究蠵龟（Caretta caretta）的汞毒性。
从自由放养的海龟采集血液，检查血液汞浓度与血浆化学成分、全血细胞计数、溶菌酶和淋巴细胞增殖之间的相关性。还从自由放养的海龟中采集淋巴细胞，并在体外暴露于甲基汞以评估增殖反应。
血液汞浓度与血细胞比容和肌酸磷酸激酶活性呈正相关，与淋巴细胞计数和天冬氨酸氨基转移酶呈负相关。在2001年和2003年的最佳检测条件下，观察到血液汞浓度与B细胞增殖之间存在离体负相关。外周血白细胞在体外暴露于甲基汞导致B细胞（0.1微克/克和0.35微克/克）和T细胞（0.7微克/克）的增殖反应受到抑制。
血液汞浓度与血细胞比容之间的正相关反映了汞物种对红细胞的亲和力高于血浆，并证明在分析全血汞含量时测量血细胞比容的重要性。在体外，甲基汞浓度约为野生捕获个体的5%时就会发生免疫抑制。这一观察结果以及在离体条件下发现的汞与淋巴细胞数量以及汞与B细胞增殖反应之间的负相关表明，在野生环境中观察到的汞浓度下，汞可能对海龟免疫功能产生微妙的负面影响。
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