Development of multi-metal interaction model for Daphnia magna: Significance of metallothionein in cellular redistribution.

Despite the great progress made in metal-induced toxicity mechanisms, a critical knowledge gap still exists in predicting adverse effects of heavy metals on living organisms in the natural environment, particularly during exposure to multi-metals. In this study, a multi-metal interaction model of Daphnia manga was developed in an effort to provide reasonable explanations regarding the joint effects resulting from exposure to multi-metals. Metallothionein (MT), a widely used biomarker, was selected. In this model, MT was supposed to play the role of a crucial transfer protein rather than detoxifying protein. Therefore, competitive complexation of metals to MT could highly affect the cellular metal redistribution. Thus, competitive complexation of MT in D. magna with metals like Pb2+ , Cd2+ and Cu2+ was qualitatively studied. The results suggested that Cd2+ had the highest affinity towards MT, followed by Pb2+ and Cu2+ . On the other hand, the combination of MT with Cu2+ appeared to alter its structure which resulted in higher affinity towards Pb2+ . Overall, the predicted bioaccumulation of metals under multi-metal exposure was consisted with earlier reported studies. This model provided an alternative angle for joint effect through a combination of kinetic process and internal interactions, which could help to develop future models predicting toxicity to multi-metal exposure.