Cytosolic Distribution of Cd2+, Cu+, and Zn2+ Among Metallothionein-Like Proteins in Lobster Hepatopancreas

Zinc and Cu metabolism in crustacea changes dramatically during the molt cycle. Metallothionein (MT) and MT-like proteins are implicated in the handling of both metal ions as well as in the detoxification of Cd. Distribution of Cd2 / Cu / and Zn2 / in cytosol and among MT-like species has been determined. Lobsters were treated to induce MT as in mammals with dexamethasone (dex) or stress from the surgical removal of a small walking toe both with and without a subsequent injection of CdCI2. Untreated tissue contains only Cu-MTII and no other significant amounts of metal-bound MTs. Exposure to dex or surgery alone causes no change in the MTs. Exposure to Cd retains the Cu-MTII and produces little Cd-MTI,II. When dex or surgery is combined with Cd2 / injection, Cu-MTII is unaffected and large quantities of Cd-MTI,II are made. Preliminary results indicate that dex or surgery induces the synthesis of apo-MT in the hepato-pancreas which serves as a site for binding cadmium.