Metallothionein induction in mussels exposed to a metal mixture

Summary

The uptake of metals such as Cd, Cu and Zn by mussels and its accumulation in their tissues is related to the binding of these metal ions to specific ligands where the metals have higher affinity. One of these ligands are the metallothioneins.

Metallothionein induction was followed in the whole soft tissues of Mytilus edulis after exposure to a metal mixture of Cd (100 μg·1^-1), Cu (50 µg·1^-1) and Zn (50 µg·1^-1). When the mussels were exposed to the same metal concentrations individually Cd and Cu induced metallothionein, while Zn exposure did not. MT induction in the whole soft tissues of the mussels exposed to the metal mixture is also observed but the induction is smaller than expected if there was a synergistic effect. This suggests that when metals are present jointly there is competition between Cd and Cu for binding MT. Subsequently MT induction is triggered by Cu and the excess of Cd in the heat-treated cytosol is bound to the newly formed MT. Data on metal concentrations suggests that different metal binding characteristics, observed specially for Cu, might be related to the difference observed on MT induction.