Association of 239Pu with lysosomes in rat, Syrian hamster, and Chinese hamster liver as studied by carrier-free electrophoresis and electron microscopic autoradiography with 241Pu.

The binding of injected monomeric plutonium in the liver of rats, Syrian hamsters, and Chinese hamsters (species which show profound differences in their ability to eliminate 239Pu from the liver) was investigated by carrier-free electrophoresis using 239Pu and electron microscopic autoradiography with 241Pu. These studies are part of a program designed to obtain a better understanding of the mechanisms of the clearance of transuranium elements from liver of different mammals and man. Between 4 and 9 days after nuclide injection, a clear correlation between the majority of the 239Pu and lysosomal enzymes was observed when the mitochondrial-lysosomal (ML) fraction of the livers was analyzed by carrier-free electrophoresis. In the two hamster species, a second 239Pu peak exists from the beginning and increases with time to comprise 50% of the total radioactivity at later times. During electron microscopic examination 4 days after 241Pu injection, beta tracks were frequently observed over globular structures resembling dense bodies in Chinese hamster liver. They were also observed frequently over chromatin-rich portions of the cell nuclei. These results, together with those from previous density gradient studies, show that lysosomes are the primary deposition site for 239Pu in the liver cytoplasm of these three rodent species. The hypothesis of a morphologic transformation of these lysosomes with time in hamster liver and of rapid bulk exocytosis of the lysosomes in rats are still possible explanations for the extreme differences in the elimination among the three species.