In this study, we investigated the facilitated depuration of non-essential elements from the tissues of Clarias gariepinus by interactions with essential elements. Fish were exposed to lead, cadmium and mercury at a range of concentrations previously detected in aquatic environments, for 28 days. Subsets of fish exposed to each of these elements were then exposed to the essential elements, such as calcium, chromium, cobalt, magnesium, potassium or zinc and untreated controls for another 28 days. After exposures, the residual concentrations of lead, cadmium and mercury in the tissues and faeces of the fish were analysed using flame atomic absorption spectrophotometry. The activities of antioxidant enzymes, such as superoxide dismutase, catalase and glutathione S-transferase in the exposed fish, were also assessed using referenced methods. The essential elements, calcium, chromium, cobalt and zinc, were found to facilitate the depuration of lead, cadmium and mercury in the exposed fish. The concentration of lead and mercury in the flesh of exposed fish decreased by 16% and 12%, respectively, after exposures to cobalt and that of cadmium decreased by 16% after exposure to zinc. The activities of the antioxidant enzymes in fish exposed to lead also decreased by at least 30%, respectively, after exposures to the essential elements. This study has shown that interactions among essential elements and non-essential elements can be beneficial, facilitating the elimination of the latter in aquatic organisms. Further studies are needed to determine the underlying mechanisms promoting this process and the possible adoption of the process to rehabilitate aquatic organisms in polluted ecosystems.

中文翻译：

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促进净化暴露鱼中有害的非必需元素

在这项研究中，我们研究了通过与必需元素的相互作用，促进了Clarias gariepinus组织中非必需元素的净化。将鱼暴露于先前在水生环境中检测到的一系列浓度的铅，镉和汞达28天。然后，将暴露于上述每种元素的鱼的子集暴露于必需元素（如钙，铬，钴，镁，钾或锌）和未经处理的对照组，再暴露28天。暴露后，使用火焰原子吸收分光光度法分析了鱼的组织和粪便中铅，镉和汞的残留浓度。超氧化物歧化酶，过氧化氢酶和谷胱甘肽S等抗氧化酶的活性还使用参考方法评估了暴露鱼中的β-转移酶。发现必需元素钙，铬，钴和锌可促进裸露鱼类中铅，镉和汞的净化。暴露于钴后，暴露的鱼肉中铅和汞的浓度分别降低了16％和12％，而暴露于锌后，镉的浓度降低了16％。暴露于铅中的鱼中的抗氧化酶活性在暴露于必需元素后也分别降低了至少30％。这项研究表明，必需元素和非必需元素之间的相互作用可能是有益的，有助于消除水生生物中的后者。