The bioinorganic chemistry of Np, Pu and Am in mammalian liver

Abstract Investigations of the sub-cellular distribution patterns of 239 Np and 237 Np in rat liver have shown that the distribution of neptunium is time and mass dependent. One hour after administration, 237 Np deposits predominantly in the cytosol, whereas at later times after exposure (24 h to 40 days) the nuclei and lysosomes are the main binding sites. In contrast, 24 h after exposure, the 239 Np was found mainly in the cytosol. Investigations in baboons with 237 Np, 239 Pu and 241 Am have shown that the cytosol was the main binding site 24 h after exposure, and that nuclei and lysosomes were involved at later times after exposure (10 days). In cytosol, 239 Pu and 241 Am were bound mainly to ferritin irrespective of the time of sacrifice. For 237 Np, it was shown, both in rats and baboons, that the radionuclide binds to two proteins soon after exposure (1–24 h) with molecular weights of 450 and 200 kDa, respectively. The former was identified as ferritin, but the latter remains unidentified. At later times (1–40 days), Np was found to be bound mainly by ferritin and by high-molecular weight compounds.