Metallothionein gene expression in arctic char (Salvelinus alpinus) following metal and PCB exposure

Full length sequences of two Arctic char (Salvelinus alpinus) metallothionein (MT) cDNAs, corresponding to MT-A and MT-B, were isolated from a λ-ZAP hepatic cDNA library. The two MT isoforms showed high similarity to rainbow trout and Atlantic salmon MT, with the coding sequences being 100% homologous to rainbow trout MT. Following characterization the MT cDNA was used to study the inducibility of Arctic char MT mRNA. Basal level expression was determined for 11 different tissues and it was observed that liver and immature gonads expressed the highest levels of MT mRNA. The inducibility of MT mRNA, by cadmium, 17β-estradiol (E2) and three PCBs (2′,4′,6′-trichloro-3-biphenylol, 2,2′,4,6,6′-pentaCB and 2,3,3′,4,4′,5′,6-heptaCB) was thereafter determined for liver, kidney and brain. While cadmium induced MT gene expression in all three organs, E2 treatment did not affect the MT mRNA levels. All three PCBs were found to result in reduced basal level MT mRNA expression.