Po Beverly H K, Wood Chris M
Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada; Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada; Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, 33149, USA.
Environ Pollut. 2021 May 1;276:116699. doi: 10.1016/j.envpol.2021.116699. Epub 2021 Feb 8.
Freshwater ecosystems are facing increasing contamination by major ions. The Multi-Ion Toxicity (MIT) model, a new tool for risk assessment and regulation, predicts major ion toxicity to aquatic organisms by relating it to a critical disturbance of the trans-epithelial potential (TEP) across the gills, as predicted by electrochemical theory. The model is based on unproven assumptions. We tested some of these by directly measuring the acute TEP responses to a geometric series of 10 different single salts (NaCl, NaSO, KCl, KSO, CaCl, CaSO, MgCl, MgSO, NaHCO, KHCO) in the euryhaline rainbow trout (Oncorhynchus mykiss) and the stenohaline goldfish (Carassius auratus) acclimated to very soft, ion-poor water (hardness 10 mg CaCO/L). Results were compared to 24-h and 96-h LC50 data from the literature, mainly from fathead minnow (Pimephales promelas). All salts caused concentration-dependent increases in TEP to less negative/more positive values, in patterns well-described by the Michaelis-Menten equation, or a modified version incorporating substrate inhibition. The ΔTEP above baseline became close to a maximum at the 96-h LC50, except for the HCO salts. Furthermore, the range of ΔTEP values at the LC50 within one species was much more consistent (1.6- to 2.1-fold variation) than the molar concentrations of the different salts at the LC50 (19- to 25-fold variation). ΔTEP responses were related to cation rather than anion concentrations. Overall patterns were qualitatively similar between trout and goldfish, with some quantitative differences, and also in general accord with recently published data on three other species in harder water where ΔTEP responses were much smaller. Blood plasma Na and K concentrations were minimally affected by the exposures. The results are in accord with most but not all of the assumptions of the MIT model and support its further development as a predictive tool.
淡水生态系统正面临着主要离子污染日益加剧的问题。多离子毒性（MIT）模型是一种用于风险评估和监管的新工具，它通过将主要离子对水生生物的毒性与鳃上皮跨膜电位（TEP）的临界干扰联系起来进行预测，这种干扰由电化学理论预测得出。该模型基于未经证实的假设。我们通过直接测量广盐性虹鳟（Oncorhynchus mykiss）和狭盐性金鱼（Carassius auratus）对10种不同单一盐类（NaCl、NaSO、KCl、KSO、CaCl、CaSO、MgCl、MgSO、NaHCO、KHCO）按几何级数配置的溶液的急性TEP反应，对其中一些假设进行了测试，这些鱼被驯化于非常软且离子含量低的水（硬度为10 mg CaCO₃/L）中。将结果与文献中的24小时和96小时半数致死浓度（LC50）数据进行了比较，这些数据主要来自黑头呆鱼（Pimephales promelas）。所有盐类都导致TEP浓度依赖性升高，变为较不负值/较正值，其模式可用米氏方程或包含底物抑制的修正版本很好地描述。除了HCO盐类外，高于基线的ΔTEP在96小时LC50时接近最大值。此外，同一物种在LC50时的ΔTEP值范围（变化1.6至2.1倍）比不同盐类在LC50时的摩尔浓度范围（变化19至25倍）更为一致。ΔTEP反应与阳离子浓度而非阴离子浓度相关。鳟鱼和金鱼之间的总体模式在定性上相似，但存在一些定量差异，并且总体上也与最近发表的关于其他三种生活在硬度更高的水中的物种的数据一致，在硬度更高的水中ΔTEP反应要小得多。血浆中的Na和K浓度受暴露影响最小。结果与MIT模型的大多数但并非全部假设一致，并支持其作为一种预测工具的进一步发展。
