Metallothionein in green sea urchins (Strongylocentrotus droebachiensis) as a biomarker for metal exposure

The object of this study was to clarify whether metallothionein (MT) in the green sea urchin (Strongylocentrotus droebachiensis) may be used as a biomarker for environmental metal stress. The concentrations of Cd, Cu, Zn and MT in the intestine and gonads of S. droebachiensis from a metal-contaminated fjord were determined. Metal concentrations were determined by ET-AAS and MT concentrations by differential pulse polarography. The method used to quantify MT was evaluated and found to be satisfactory for intestinal samples, but failed to remove high-molecular weight (HMW) sulfhydryl-rich components in gonads. Both intestine and gonads of S. droebachiensis collected from a metalcontaminated area contained higher concentrations of Cd and Zn than sea urchins collected at a clean reference site. Metallothionein in sea urchin intestine related to both Cd and Zn in this tissue. In contrast, sex differences appeared to a large extent to determine metal-binding protein (MBP) concentrations (including HMW components) in gonads. In conclusion, MT in sea urchin intestine is a promising candidate as an invertebrate biomarker for exposure to Cd and Zn. In this species, MT in gonads appears not to be appropriate as a biomarker.