Cadmium induction of metallothionein isoforms in juvenile and adult mussel (Mytilus edulis)

Isoforms of metallothionein in the digestive gland of control and experimentally Cd-exposed mussels Mytilus edulis (200 mg l-1 Cd2+ and 400 mg l-1 Cd2+; 20 days) were studied using the RT-PCR. In addition, glutathione S-transferase (GSTpi) primers were designed in order to evaluate the reduction in the antioxidant defence systems (glutathione) accompanying the ageing process in the same organisms. Following experimental exposure, an accumulation of Cd was observed in the digestive gland of exposed mussels, both adults and juveniles, up to 500 times higher than in control. An induction of the dimeric form MT20 II was detected in 400 mg l-1 exposed mussels, as well as a visible inhibition of the monomeric form MT10 IV. After 20 days exposure juveniles expressed increased GSTpi compared with adults. Results reveal individual variation of both metallothioneins and GSTpi expression among control and Cd2+ exposed mussels of different ages. The ecotoxicological significance of MT utilisation in biomonitoring of seawater for trace metals has been considered in light of these results.