Changes in metallothionein mRNA and protein after sublethal exposure to arsenite and cadmium chloride in juvenile winter flounder

Juvenile winter flounder (Pleuronectes americanus) from a Long Island Sound site within the Niantic River region contain elevated levels of liver As and Cd. Previous work in mammals suggests that a reduced species of As. NaAs3-, is as potent a metallothionein (MT) inducer as CdCl2. We investigated whether this is also the case in winter flounder by subcutaneously exposing juveniles to a sublethal range of NaAs3+ (0, 0.38. 0.75, and 1.5 mu mol/g fish) or CdCl2 (0, 0.045, 0.09. and 0.18 mu mol/g fish). Of the two, CdCl2 was the more potent MT inducer, with an 8-fold lower molar equivalent causing a 3-fold higher response. Both metals rapidly induced MT protein within 24 h of exposure, but only the highest dose of CdCl2 elicited a significant increase in MT mRNA. The magnitude of the MT protein response to CdCl2 (7.25-fold) demonstrates that elevated liver As and Cd do not narrow the MT response window in juvenile flounder from the Niantic River region. These fish have relatively low liver MT protein levels (46 mu g/g) and will be a useful reference population for future metal impact studies within Long Island Sound.