Effect of a polymetallic mixture on metal accumulation and metallothionein response in the clam Ruditapes decussatus

The toxic effects of metals are related to changes in natural physiological and biochemical processes in organisms, which are not easily detected. Marine invertebrates developed strategies to survive in the presence of toxic metal levels, by the removal of these compounds from the soluble fraction of the cell through different processes, including the synthesis of metallothionein (MT). To better understand the effect of Cd, Cu and Zn in MT response it is important to consider that in their natural environment these metals are normally mixed. The exposure to a metal mixture result in toxicological interactions that produce different biological responses when compared to the effects of a single metal exposure. The aim of this study was to assess metal accumulation and MT response in different tissues of the clam Ruditapes decussatus exposed to a mixture of sublethal Cd, Cu and Zn concentrations. Kinetic models were applied to determine metal uptake and loss to better predict and understand the detoxification mechanisms in this species. The kinetic model showed that the effect of this polymetallic exposure compared to a single exposure to these metals caused different metal uptake and loss rates in several tissues. Moreover, the exposure of R. decussatus to a polymetallic mixture caused an increase in MT induction compared to a single metal exposure. This is probably related to the interaction between the different metals and their different affinity to this protein. Metal interactions within aquatic organisms are very important in MT synthesis and the effect of polymetallic mixtures in the environment must be taken into account in field studies.

FCT PhD Grant (CIÊNCIA/BD/2541/93)

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