Internal distribution and micro-localisation of metals in the bivalve Corbicula fluminea

Titre du congrès :SETAC Europe 16th Annual Meeting Ville du congrès :La Hague Date du congrès :11/05/2006

For ecological risk assessment of metals, the internal distribution of the studied element in living organisms at various organizational levels allows to characterize the critical residue (internal dose) that may act as a trigger for a given effect. Experiments have been focused on bivlaves exposed to various levels of uranium from direct pathway. Subcellular fractionation and histological studies with TEM-EDX analysis were then performed to identify the biological target of uranium. The U total quantities in target organs depend on the exposure conditions while the subcellular U distribution (80% of U in the insoluble fraction) remained identical whatever the treatment. In bivalves gills, U was observed in subcellular granules, suggesting a potential source of α-irradiation for organelles, specially the mitochondria. The purity of the subcellular fraction was checked by TEM observations and our microlocalisation results were confirmed by comparing the TEM-EDX results with those obtained applying another fixation treatment of the biological sample (high pressure freezing).