Subcellular fraction associated to radionuclide analysis in various tissues: Validation of the technique by using light and electron observations applied on bivalves and uranium

Laboratory of Radioecology and Ecotoxicology, Institute for Radiological Protection and Nuclear Safety, DEI/SECRE/LRE, Cadarache, Bât. 186, BP. 3, 13115 St-Paul-lez-Durance Cedex, France

Abstract

The metal bioaccumulation levels in target-organs associated with microlocalisation approaches at the subcellular level provide information for the understanding of the metabolic metal cycle. These findings could be used to select relevant biomarkers of exposure and to focus on specific contaminated organelles to study potential biological effects. Moreover, the metal accumulated in the cytosol fraction can be bound to macromolecules in order to be eliminated and/or to induce a potential cellular effect. Tissular distribution, transfer efficiency from water and subcellular fractionation were investigated on the freshwater bivalve, Corbicula fluminea after uranium aqueous exposure. The subcellular fractionation was performed while measuring associated uranium to each cellular different fraction as follows: cellular debris and nuclei, mitochondria and lysosomes, membranes, microsomes and cytosol. In our experimental conditions, the accumulation in the cytosol fraction was low and more than 80 % of the total uranium in gills and visceral mass was accumulated in the insoluble fraction. Main results presented in this paper come from light and electron microscope observations of subcellular fractions (nuclei/debris and lysosomes/mitochondria) in order to validate the efficiency of the fractionation technique. An adaptation of the fractionation technique is proposed. This set of data confirms high differences of fractionation efficiency as a function of used fractionation technique and organs/biological model.