Langston W J, Chesman B S, Burt G R, Pope N D, McEvoy J
Marine Biological Association, Citadel Hill, Plymouth, UK.
Mar Environ Res. 2002 Apr;53(3):263-93. doi: 10.1016/s0141-1136(01)00113-1.
The purpose of this study was to examine the role of the cysteine-rich protein metallothionein (MT) in the detoxification and metabolism of metals in livers of eels Anguilla anguilla from the Thames Estuary, and to assess the value of MT measurements in environmental monitoring. Hepatic MT levels and associated metal concentrations were determined in A. anguilla collected on three occasions during 1998 at sites along the tidal Thames (from freshwater to the sea) and also from a reference site (Tamar Estuary) in southwest England. MT was present at basal levels of 2 mg g(-1) dry weight (dw), predominantly in association with the essential metals Cu and Zn. MT concentrations were variable within each eel 'population' but were generally highest (up to 11 mg g(-1) in individual eels) at the more contaminated upper- and mid-estuarine sites in the Thames (e.g. Brentford and Kew). Lowest MT levels were those in eels from Blythe Sands at the mouth of the estuary. Season, sex, reproductive status and salinity may have influenced MT levels to some extent, although metals were the most significant factor. Hepatic MT concentrations were highly correlated with associated metal burdens (Zn, Cu, Ag and Cd),--notably reflecting Cu and Ag enrichment in the upper- and mid-estuary. With the exception of Zn, metals in the supernatant fraction of eel livers were primarily associated with MT. Proportions of Cu, Ag and Cd bound to MT increased as a function of accumulated metal burdens, with no indication of saturation. Thus, despite causing induction of MT, excess bioavailable Cu, Ag and Cd appear to be successfully detoxified in eels over the range of environmental contamination encountered along the Thames Estuary. Paradoxically, it may be argued from conventional doctrine that the presence of raised levels of MT, at upstream sites, constitutes a response to contamination and, by definition, signals that the fish are affected by metals; however, obvious signs of deleterious effects were not detected. Superficially, from liver MT data, it would seem that eel populations have become biochemically adapted to metal contamination. The approach tested here has proved viable in helping to interpret trends in bioavailability and the toxicological significance of accumulated metal burdens in Thames eels. A. anguilla is a common inhabitant of estuarine and fresh waters throughout Europe, and related species occur world wide. Therefore, determination of hepatic MT (and associated metals) in eels could be useful for monitoring responses to metal exposure and environmental quality on a much broader basis. Ideally these determinations should be performed in tandem with other sublethal-effects measurements to maximise information.
本研究的目的是检测富含半胱氨酸的金属硫蛋白（MT）在泰晤士河口欧洲鳗鲡肝脏中金属解毒和代谢中的作用，并评估MT测量在环境监测中的价值。在1998年分三次采集了泰晤士河潮汐段（从淡水到海洋）沿线各点以及英格兰西南部一个参考点（塔马河口）的欧洲鳗鲡，测定其肝脏MT水平及相关金属浓度。MT以2 mg g⁻¹干重（dw）的基础水平存在，主要与必需金属铜和锌结合。MT浓度在每个鳗鲡“群体”内存在差异，但在泰晤士河受污染更严重的河口上段和中段站点（如布伦特福德和基尤）通常最高（个别鳗鲡中可达11 mg g⁻¹）。河口口处布莱斯沙滩的鳗鲡MT水平最低。季节、性别、生殖状态和盐度可能在一定程度上影响了MT水平，不过金属是最主要的因素。肝脏MT浓度与相关金属负荷（锌、铜、银和镉）高度相关，尤其反映了河口上段和中段铜和银的富集情况。除锌外，鳗鲡肝脏上清液部分中的金属主要与MT结合。与MT结合的铜、银和镉的比例随累积金属负荷增加而增加，没有饱和迹象。因此，尽管导致了MT的诱导，但在泰晤士河口所遇到的环境污染范围内，过量的生物可利用铜、银和镉在鳗鲡中似乎能成功解毒。矛盾的是，按照传统理论可能会认为，上游站点MT水平升高是对污染的一种反应，从定义上讲表明鱼类受到了金属影响；然而，并未检测到有害影响的明显迹象。从表面上看，根据肝脏MT数据，鳗鲡种群似乎已经在生化方面适应了金属污染。这里所测试的方法已证明在帮助解释生物可利用性趋势以及泰晤士河鳗鲡中累积金属负荷的毒理学意义方面是可行的。欧洲鳗鲡是欧洲河口和淡水的常见居民，相关物种在世界各地都有。因此，测定鳗鲡肝脏中的MT（以及相关金属）对于在更广泛基础上监测对金属暴露的反应和环境质量可能是有用的。理想情况下，这些测定应与其他亚致死效应测量同时进行，以获取最多信息。
