Metallothionein isoforms in Mytilus edulis (Mollusca, Bivalvia): Complementary DNA characterization and quantification of expression in different organs after exposure to cadmium, zinc, and copper

Reverse transcriptase-polymerase chain reaction has been used to isolate on e metallothionein isoform (MT-20) complementary DNA from RNA extracted from mussel gill. Another cDNA, isolated by screening a Mytilus edulis cDNA man tle library using the first cDNA as probe, codes for the MT-10 IV isoform. Northern blot analysis using these cDNAs revealed different expression of t hese isoforms. Induction with CdCl2 caused high levels of both MT messenger RNAs, especially the MT-20, which was induced by cadmium salt but not by z inc and copper salts. An induction of MT-10 was detected with ZnCl2. These results show that genes encoding distinct MT isoforms are differentially re gulated by heavy metals.