甲基汞在褐牙鲆幼鱼体内蓄积的组织特异性及其对免疫功能和生长的毒性作用

Tissue-specific bioaccumulation of methylmercury(MeHg) and its toxicity to the immunologic function and growth of juvenile flounder Paralichthys olivaceus

甲基汞(MeHg)对鱼类多种生命过程存在极强的毒性作用,但有关其对海水鱼类免疫功能的毒性作用研究较少。本文利用实验毒理学方法研究了MeHg(暴露浓度0.0,0.1,1.0,10.0,20.0μg/L;暴露时间30天)在褐牙鲆(Paralichthys olivaceus)幼鱼组织(鳃、肝脏和脾脏)中的蓄积特征及其对幼鱼的四种免疫功能生物指示物(溶菌酶LZM、酸性磷酸酶ACP、碱性磷酸酶AKP和免疫球蛋白M IgM)和生长的毒性作用。结果表明,幼鱼体内MeHg蓄积量具有显著的浓度依赖性和组织特异性,各组织对MeHg的蓄积能力总体上呈现肝脏>鳃>脾脏的趋势;四种免疫功能生物指示物(活性或含量)对不同MeHg浓度暴露的响应方式各异,且具有显著的组织特异性;MeHg达到一定暴露浓度后显著抑制幼鱼的生长。总体而言,MeHg在褐牙鲆幼鱼体内蓄积,对其产生免疫毒性,并抑制幼鱼的生长。此外,ACP、AKP和LZM等免疫性指标能较好的反映对MeHg暴露的浓度依赖关系和组织特异性,可作为海水环境中MeHg污染风险评估和生物毒性分析的潜在生物指示物。

Methylmercury(MeHg)poses a great threat to various life processes of fish,but its toxic effect on the immune function of marine fish is rarely studied.In this study,a laboratory toxicity test(30 days)was conducted to investigate the bioaccumulation of MeHg in three tissues(gills,liver,and spleen)and its toxicity to four immunological indicators(lysozyme(LZM),acid phosphatase(ACP),alkaline phosphatase(AKP),and immunoglobulin M(IgM))and the growth of juvenile flounder Paralichthys olivaceus.In the test,the nominal exposure concentrations of MeHg were 0.0(control),0.1,1.0,10.0,and 20.0μg/L.The results revealed that the bioaccumulation of MeHg was positively concentration-dependent and tissue-specific,with an overall bioaccumulation ranking of liver>gills>spleen.The activities or contents of the four immunological indicators responded differently to MeHg exposure,depending on indicators and tissues.The MeHg exposure of over a certain concentration(e.g.,20.0μg/L)could significantly inhibit the growth of the fish.Generally,MeHg accumulated in biological tissues of flounder juveniles,which produced immunotoxicity and inhibited the growth of juveniles.In addition,changes in activities or contents of ACP,AKP,and LZM well reflected the concentration-dependent and tissue-specific responses to MeHg exposures and therefore can be used as potential bioindicators for assessing the risk of MeHg pollution and toxicity to organisms in seawater.