Schlenk D, Zhang Y S, Nix J
Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205, USA.
Ecotoxicol Environ Saf. 1995 Aug;31(3):282-6. doi: 10.1006/eesa.1995.1075.
Metallothioneins (MTs) are low-molecular-weight cytosolic proteins that are induced by cellular stress as well as exposure to various heavy metals including mercury. Excessive residues of mercury have recently been identified in various fish species of the lower Ouachita River system in Arkansas. Fillets of mature largemouth bass (Micropterus salmoides) collected from Woodard Lake, an ox-bow lake of the Ouachita River, possessed muscle residues of mercury ranging from 0.3 to 1.0 ppm (micrograms/g). To assess the usefulness of using MT expression as a biomarker of mercury exposure, livers and fillets were obtained from feral bass of Woodard Lake. Ouachita served as a control site having mercury residues below detection. Analyses using a ribonuclease protection assay with winter flounder MT cDNA revealed that bass had significantly elevated levels of MT mRNA which correlated (r2 = 0.756) with the levels of mercury in muscle fillets. To further explore the water quality of Woodard Lake, 10 juvenile channel catfish were housed in cages and placed where feral collections were made in both sites for 2 weeks. Mercury was not detected in muscle or liver and no significant difference in hepatic MT mRNA was observed. These data demonstrate that MT mRNA expression can be used as a tool to assess exposure to heavy metals and suggest that the elevated levels of mercury in large predatory fish may be due to trophic magnification rather than a single point-source exposure.
金属硫蛋白（MTs）是低分子量的胞质蛋白，可由细胞应激以及接触包括汞在内的各种重金属诱导产生。最近在阿肯色州沃希托河下游水系的各种鱼类中发现了过量的汞残留。从沃希托河的牛轭湖伍达德湖采集的成熟大口黑鲈（Micropterus salmoides）鱼片，其肌肉中的汞残留量为0.3至1.0 ppm（微克/克）。为了评估将MT表达用作汞暴露生物标志物的有效性，从伍达德湖的野生鲈鱼中获取了肝脏和鱼片。沃希托作为对照地点，汞残留量低于检测限。使用与冬比目鱼MT cDNA的核糖核酸酶保护分析表明，鲈鱼的MT mRNA水平显著升高，这与肌肉鱼片中的汞含量相关（r2 = 0.756）。为了进一步探究伍达德湖的水质，将10条幼年沟鲶放在网箱中，放置在两个地点进行野生样本采集的地方2周。在肌肉或肝脏中未检测到汞，并且未观察到肝脏MT mRNA有显著差异。这些数据表明，MT mRNA表达可作为评估重金属暴露的工具，并表明大型掠食性鱼类中汞含量的升高可能是由于营养级放大，而非单点源暴露所致。
