Department of Environmental and Molecular Toxicology, North Carolina State University, Box 7633, Raleigh, North Carolina 27695, USA.
Environ Toxicol. 2012 May;27(5):268-76. doi: 10.1002/tox.20639. Epub 2010 Aug 19.
Freshwater mussels are an imperiled fauna exposed to a variety of environmental toxicants such as lead (Pb) and studies are urgently needed to assess their health and condition to guide conservation efforts. A 28-day laboratory toxicity test with Pb and adult Eastern elliptio mussels (Elliptio complanata) was conducted to determine uptake kinetics and to assess the toxicological effects of Pb exposure. Test mussels were collected from a relatively uncontaminated reference site and exposed to a water-only control and five concentrations of Pb (as lead nitrate) ranging from 1 to 245 μg/L in a static renewal test with a water hardness of 42 mg/L. Endpoints included tissue Pb concentrations, hemolymph Pb and ion (Na⁺, K⁺, Cl⁻, Ca²⁺) concentrations, and Na⁺, K⁺-ATPase enzyme activity in gill tissue. Mussels accumulated Pb rapidly, with tissue concentrations increasing at an exposure-dependent rate for the first 2 weeks, but with no significant increase from 2 to 4 weeks. Mussel tissue Pb concentrations ranged from 0.34 to 898 μg/g dry weight, were strongly related to Pb in test water at every time interval (7, 14, 21, and 28 days), and did not significantly increase after day 14. Hemolymph Pb concentration was variable, dependent on exposure concentration, and showed no appreciable change with time beyond day 7, except for mussels in the greatest exposure concentration (245 μg/L), which showed a significant reduction in Pb by 28 days, suggesting a threshold for Pb binding or elimination in hemolymph at concentrations near 1000 μg/g. The Na⁺, K⁺-ATPase activity in the gill tissue of mussels was significantly reduced by Pb on day 28 and was highly correlated with tissue Pb concentration (R² = 0.92; P = 0.013). The Na⁺, K⁺-ATPase activity was correlated with reduced hemolymph Na⁺ concentration at the greatest Pb exposure when enzyme activity was at 30% of controls. Hemolymph Ca²⁺ concentration increased significantly in mussels from the greatest Pb exposure and may be due to remobilization from the shell in an attempt to buffer the hemolymph against Pb uptake and toxicity. We conclude that Na⁺, K⁺-ATPase activity in mussels was adversely affected by Pb exposure, however, because the effects on activity were variable at the lower test concentrations, additional research is warranted over this range of exposures.
淡水贻贝是一种处于危险境地的动物，它们暴露在各种环境毒物中，如铅（Pb）。迫切需要研究来评估它们的健康和状况，以指导保护工作。我们进行了一项为期 28 天的实验室毒性测试，用 Pb 和成年东方椭圆贻贝（Elliptio complanata）进行测试，以确定摄取动力学，并评估 Pb 暴露的毒理学效应。测试贻贝是从一个相对无污染的参考地点收集的，在一个静态更新测试中，用硬度为 42 毫克/升的水暴露于 5 个 Pb 浓度（以硝酸铅计），浓度范围为 1 至 245 微克/升。终点包括组织中的 Pb 浓度、血淋巴中的 Pb 和离子（Na ⁺ 、K ⁺ 、Cl ⁻ 、Ca ² ⁺ ）浓度，以及鳃组织中的 Na ⁺ 、K ⁺ -ATP 酶活性。贻贝迅速积累 Pb，组织浓度随暴露浓度呈依赖性增加，在第 2 周至第 4 周之间没有显著增加。贻贝组织中的 Pb 浓度范围为 0.34 至 898 微克/克干重，与每个时间间隔（7、14、21 和 28 天）的试验水中的 Pb 密切相关，并且在第 14 天后没有显著增加。血淋巴中的 Pb 浓度是可变的，取决于暴露浓度，并且除了暴露浓度最大（245 微克/升）的贻贝外，在第 7 天后，Pb 浓度没有明显变化，在浓度接近 1000 微克/克时，血淋巴中的 Pb 结合或消除可能存在一个阈值。在第 28 天，Pb 显著降低了贻贝鳃组织中的 Na ⁺ 、K ⁺ -ATP 酶活性，并且与组织中的 Pb 浓度高度相关（R ² = 0.92；P = 0.013）。当酶活性降至对照的 30%时，与最大 Pb 暴露下血淋巴中 Na ⁺ 浓度降低相关。在最大 Pb 暴露下，贻贝的血淋巴 Ca ² ⁺ 浓度显著升高，这可能是由于从贝壳中重新动员以试图缓冲血淋巴对 Pb 摄取和毒性的影响。我们得出结论，贻贝的 Na ⁺ 、K ⁺ -ATP 酶活性受到 Pb 暴露的不利影响，然而，由于在较低的测试浓度下对活性的影响是可变的，因此需要在这个暴露范围内进行更多的研究。
