Biokinetics of a transuranic (238PU) and a rare earth element (152Eu) in the lobster (Homarus gammarus): transfer mechanisms (accumulation and detoxification) in organs and at the cellular level

The work presented here is an experimental investigation of the biokinetics of transfer of a transuranic and a rare earth element (238Pu and 152Eu) in the lobster Homarus gammarus. The study of 238Pu biokinetics forms part of a wider framework of research concerning the transfer of transuranic elements in marine species, while the study of 152Eu is carried out with a view to supporting the analogy between the behaviour of transuranics and rare earths in living organisms. Exactly the same experimental protocol, based on techniques from various disciplines (biology, biochemistry and metrology), was used to Investigate the biokinetics of transfer of these two radionuclides. The Individual lobsters were radiolabelled by means of one-shot or chronic ingestion of spiked meals. As the first approach, the kinetics and transfer mechanisms were studied In whole animal samples and in different organs distinct series of pathways through the different organs were identified in the case of both radionuclides, being mainly linked to digestive processes induced by the meal as well as the transport function of hemo-lymph in this way, the Important role of the digestive gland was picked out, with two of four cellular types displaying a successive involvement In the fixation and then the retention of the studied radionuclides. As a corroborative approach, the digestive gland was subjected to a more detailed investigation with the aim of describing the mechanisms of Incorporation and elucidating transfer processes at the cellular and molecular levels. 238Pu is preferentially partitioned into the cytosol, where it is associated with various constituents such as ferritin (iron-storing protein). 152Eu is more diffusely distributed in the hepato-pancreatic cells, while the lysosomes appear to play a more important role during transfer. The results obtained in this study, both on the macroscopic scale (i.e. the whole animal and different organs) as well as the cellular and molecular levels, are used to compare the behaviour of the two radionuclides and discuss the biokinetics of transfer processes in the light of published data concerning transuranics elements, In particular americium. (author)