Long-term 238Pu and 239Pu retention and organ distribution in mice at low doses

The 238Pu and 239Pu distribution in femur, liver, kidneys and testes and the retention function in the skeleton and liver have been studied in about 50 (C57 BL X C3H) F1 male mice. Groups of about 5-10 male mice were sacrificed from 10 to 800 days postinjection to cover their entire life span. All animals were injected intravenously with monomeric solutions of plutonium (1% trisodium citrate at pH 6.5) at doses of the order 7-15 kBq/kg body weight. The low levels of plutonium have been measured by direct counting in the entire animals and by radiochemical methods in the various tissues and organs. Significant differences between 238Pu and 239Pu were not observed at the injected doses used. The following proportions of the injected doses are retained in mice at the end of their life span: 12% in the skeleton, 0.7% in the liver, 0.1% in kidneys and 0.06% in gonads. Furthermore, the data have shown that (1) the long-term component of the plutonium skeleton retention in mice has a biological half-time that is much longer than their average life span; and (2) the long-term component of the plutonium liver retention in mice has a biological half-time of about 350 days.