CHANGES IN METALLOTHIONEIN MESSENGER-RNA 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 spec ies of As. NaAs3-, is as potent a metallothionein (MT) inducer as CdCl 2. 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. Bo th 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) demonst rates that elevated liver As and Cd do not narrow the MT response wind ow 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 usef ul reference population for future metal impact studies within Long Is land Sound.