Nutritional Sciences Division, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
J Exp Biol. 2012 Mar 1;215(Pt 5):822-32. doi: 10.1242/jeb.062505.
To negate the toxicity of labile intracellular metals, some aquatic organisms partition metals into specific subcellular locations for detoxification, namely the soluble heat-stable cytosol and insoluble metal-rich granules. The aim of the present study was to characterise these subcellular storage sites in the freshwater crustacean Gammarus pulex (Linnaeus) following in situ exposures upstream (Drym, low metal) and downstream (Relubbus, elevated metal) of copper- and zinc-rich inflows into the River Hayle (Cornwall, UK). In the cytosol of gammarids exposed at Relubbus, copper and zinc associated to a 7.5-kDa metallothionein-like protein (MTLP) that was largely absent from gammarids prior to exposure. Exposure at Relubbus caused MTLP concentrations to increase 4- to 5-fold between days 2 and 4, indicating an induction response to increased labile intracellular metal. On day 16, spherical calcium-rich granules (0.5-2.5 μmol l(-1)) were visualised and analysed in the posterior caeca of gammarids exposed at both sites. Following exposure at Relubbus, granules contained trace amounts of copper, but zinc was absent. Granules in gammarids exposed at Drym contained no detectable copper or zinc. Granule formation appeared to be independent of exposure. Within the posterior caeca, granules have been associated with calcium storage during the crustacean molt, rather than in detoxification of trace metals. However, the granular copper burden appeared to follow environmental Cu availabilities. Thus, we describe Cu sequestration within molt-cycle calcium storage granules. As both MTLP concentrations and granule formation in crustaceans are affected upon by molting, we hypothesise that detoxification might impact upon this existing process.
为了降低不稳定细胞内金属的毒性，一些水生生物将金属分配到特定的亚细胞位置进行解毒，即可溶的热稳定胞质溶胶和不可溶的富含金属的颗粒。本研究的目的是在铜和锌丰富的溪流流入的上游（Drym，低金属）和下游（Relubbus，高金属）对淡水甲壳类动物秀丽隐杆线虫（Linnaeus）进行原位暴露后，对这些亚细胞储存部位进行特征描述。在 Relubbus 暴露的栉虾中，铜和锌与一种 7.5 kDa 的金属硫蛋白样蛋白（MTLP）结合，而在暴露前栉虾中这种蛋白基本不存在。在 Relubbus 暴露期间，MTLP 浓度在第 2 天到第 4 天之间增加了 4 到 5 倍，表明对增加的不稳定细胞内金属有诱导反应。在第 16 天，在暴露于两个地点的栉虾的后肠中观察到并分析了富含钙的球形颗粒（0.5-2.5 μmol l(-1))。在 Relubbus 暴露后，颗粒中仅含有痕量的铜，但锌不存在。在在 Drym 暴露的栉虾中，颗粒中没有检测到铜或锌。颗粒的形成似乎与暴露无关。在后肠中，颗粒与甲壳类动物蜕皮期间的钙储存有关，而不是与痕量金属的解毒有关。然而，颗粒中的铜负荷似乎与环境中的 Cu 可利用性有关。因此，我们描述了 Cu 被螯合到蜕皮周期中的钙储存颗粒中。由于 MTLP 浓度和甲壳类动物颗粒的形成都受到蜕皮的影响，我们假设解毒可能会影响到这个现有过程。
