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(22-53) Metallothionein immunohistochemical levels in liver and gill target cell types of cadmium-exposed turbot (Scophthalmus maximus). Alvarado, Nelva1, Buxens, Amaya2, Amaral, Andre2, Mazon, Luis2, Cancio, Ibon1, Marigomez, Ionan*,1, Soto, Manu1, 1 Dept. of Zoology and Animal Cell Dynamics. Univ. Basque Country., Bilbo., Basque Country (Spain)2 Dept. of Animal Biology and Genetics. Univ. Basque Country., Bilbo., Basque Country (Spain) ABSTRACT- Studies involving aquatic animals have suggested a central role for metallothioneins (MT) in the regulation and detoxification of essential and nonessential metals. Aquatic organisms induce MT synthesis to acquire tolerance and/or resistance to metal exposure. Antibodies raised against MT may be useful tools to indicate the degree of MT induction and to clarify their cellular localisation. Turbots were exposed to 1 and 10 ppm of Cd, liver and gills being excised after 1 h, 1 and 7 d of exposure and after 14 d of depuration. Samples were fixed in Carnoy and embedded in paraffin. Tissue sections were immunostained with antiCod MT and MT levels were quantified by image analysis. Other samples were homogenised and differential centrifugation applied to obtain different cell fractions. MTs were quantified in such fractions by difference pulse polarography (DPP). Immunohistochemical MT levels increased with dose and exposure time in branchial chloride cells (CC) and in hepatocytes. A weak immunohistochemical reaction was observed in the other cell types in the gill epithelium. This means that immunohistochemistry is the only way of accurately measuring MT induction in the gill since DPP measures MT in the whole tissue where the cells other than CCs mask the response. As shown by DPP, MTs are localised in cytosolic and lysosomal fractions in the liver. Highest concentrations are localised in the cytosol. In conclusion, immunohistochemical levels of MT quantified in hepatocytes and in CCs of turbot can be considered as useful biomarkers of metal exposure. *We are indebted to Culmanor SA and NIVA (Norway) for supplying turbot and antibody. Funded by the Ministry of Science (AMB99-0324). Key words: metallothioneins, immunohistochemistry, exposure biomarkers, turbot |
