Tissue-specific cadmium accumulation, metallothionein induction, and tissue zinc and copper levels during chronic sublethal cadmium exposure in juvenile rainbow trout

Juvenile rainbow trout, on 3% of body weight daily ration, were exposed to 0 (control) or 3 mug/L Cd (as Cd(NO3)(2) . 4H(2)O) in moderately hard (140 mg/L as CaCO3), alkaline (95 mg/L as CaCO3, pH 8.0) water for 30 days. Part icular attention focused on Cd burden in tissues (gills, liver, kidney, and whole body) and induction of metallothionein (MT) in gills, liver, and kid ney during chronic Cd exposure. Mortality in Cd-exposed fish was minimal (s imilar to 10%), and no growth effects occurred over the 30-day exposure. Cd accumulated in a time-dependent fashion to 9 times (gills), 3 times (liver ), 20 times (kidney), 2 times (carcass), and 2 times (whole body) control l evels by 30 days; absolute concentrations were in the order kidney > gill > liver > whole body > carcass. Tissue (gills, liver, and kidney) Zn and Cu burdens were not altered by chronic exposure to 3 mug/L Cd. MT concentratio ns in all tissues increased over the 30 days of Cd exposure, but the increa ses were much less than those of Cd on a molar binding site basis. Absolute MT concentrations were in the order liver > kidney > gill, but relative in creases were greatest in kidney (fourfold), followed by gills (twofold) and liver (1.3-fold). MT levels were sufficient to bind all Cd in gill, liver, and kidney under control conditions. and after chronic Cd exposure remaine d sufficient in liver and kidney, but not in gills. Total metal levels (Cd + Zn + Cu) greatly exceeded MT binding capacity in all tissues under all co nditions.