The influence of radiation dose distribution on the frequency of 239Pu-induced liver
tumors was evaluated in the Chinese hamster. Different concentrations of 239Pu
citrate 239PuO2 particles of known sizes were injected intravenously via the jugular vein. About 60% of the injected 239Pu
citrate was deposited in the liver and 40% in the bone. The 239Pu
citrate was rather uniformly distributed throughout the liver parenchyma. Injected
plutonium oxide particles were taken up by the reticuloendothelial system with 90% of the body burden deposited in the liver. The 239PuO2 particles were localized in the Kupffer cells and produced nonuniform dose distributions that were dependent on particle size. There was an activity- and dose-dependent increase in the incidence of total liver parenchymal cell
tumors following injection with either
plutonium particles or
citrate. For animals that received 14.0-, 2.7-, 0.3-, and 0.04-Gy dose to liver from 239Pu
citrate the cumulative
tumor incidence was 39, 32, 5, and 0%, respectively. Animals that were injected with the 0.24 micron 239PuO2 particles had doses of 42.0, 7.2, and 0.8 Gy to the liver and
tumor incidences of 34, 26, and 5%, respectively.
Plutonium citrate also produced
hemangiosarcomas of the liver and
tumors in bone and bone marrow. The latent period for liver
tumor appearance in animals exposed to 239Pu
citrate or 239PuO2 particles increased as the injected activity decreased. For animals injected with a similar total activity (7.4 Bq/g), the lifetime cumulative liver
tumor incidence was similar for animals exposed to either 239Pu
citrate (32%) or 239PuO2 (26%). There was little effect of particle size on liver
tumor incidence. These data indicate that, in Chinese hamster liver, local radiation dose distribution is less important in altering
tumor incidence than injected activity or average dose. However, the more uniform irradiation from 239Pu
citrate administration was more effective in
cancer production than the nonuniform irradiation from 239PuO2 particles.