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(T/EH015) Metallothioneins and metal levels in mussel digestive cells as realistic biomarkers of metal exposure*. Zaldibar, Beñat1, Buxens, Amaia1, Alvarado, Nelva1, Papadaki, Maria1, Zorita, Izaskun1, Mazón, Luis1, Marigómez, Ionan1, Soto, Manu1, 1 ABSTRACT- There is a need to develop sensitive and easy-to-apply (exposure and effect) biomarkers in marine biomonitoring programmes. Metallothioneins (MT) are ubiquitous, low-molecular-weight proteins which participate in metal homeostasis and protection against metal toxicity in molluscs. The applicability of MT induction as biomarker is currently under discussion. The MT-metal complexes in digestive cell lysosomes of mussels by autometallography and automated image analysis (volume density of autometallographed Black Silver Deposits, BSD extent) may be considered as exposure biomarkers. The aim of this study was to assess the reliability of using combined measurements such as MT-levels and BSD extent as exposure biomarkers in biomonitoring programmes. Mussels were exposed to 10 Key words: metallothioneins, biomarkers, difference pulse polarography, autometallography |
g Cd, Cu and Zn/l, digestive glands excised after 1 hr, 1 day and 7 days of exposure and after 21 d of depuration. Samples were (a) fixed in Carnoy and routinely processed to quantify BSD extent and cell-type replacement, (b) homogenised using cytosolic fractions to quantify MT by difference pulse polarography, and (c) digested to estimate metal concentrations (AAS). MT levels increased at increasing exposure-level. Concomitantly, metal concentrations measured in the digestive gland increased at increasing exposure-level and were correlated with the volume density of BSD extent quantified in digestive cell lysosomes. BSD extent and metal concentrations were reduced after depuration period. It can be concluded that studied biomarkers could be used in biomonitoring programmes since reflect slight changes of metal bioavailability. * Funded by UPV/EHU (076.310-EB072/99) and Spanish Ministry of Science and Culture (AMB99-0324, CICYT and PB97-0629, DGES).