Factors affecting hepatic metallothionein levels in marine flatfish

Tissue metallothionein concentrations in marine flatfish have been evaluated as a potential indicator of metal pollution in the sea. The effect on metallothionein in flatfish of agents known to induce its synthesis in mammals was examined. (1) Metals. Intraperitoneal injection of zinc into plaice ( Pleuronectes platessa) gave rise to a rapid and large increase in hepatic metallothionein. This had a half-life of about a month. In contrast, dietary zinc at a concentration of 1000 mg/kg (dry wt) did not significantly increase hepatic nor renal metallothionein levels in the turbot ( Scophthalmus maximus). (2) Stress. There was no effect on hepatic metallothionein in plaice exposed to the stress of capture nor the injection of endotoxin, cortisol, dexamethasone or turpentine. Seasonal variation was found in female plaice. During the breeding season mature fish had occasional very high concentrations of hepatic metallothionein, possibly associated with egg development.