Whole-body Autoradiographic Studies on Plutonium Metabolism as Affected by Its Physico-chemical State and Route of Administration

Abstract A comparative investigation of autoradiograxns was carried out on specimens obtained from animals administered “monomeric” or “polymeric” plutonium. Results were compared with those obtained from animals administered metabolically stable reference particles of known particle size. In addition to whole-body autoradiography and measurements of whole-body retention by counting of L-X rays, blood clearance was also examined, and the modification of plutonium distribution and excretion by DTPA. Following intravenous injection, the blood clearance of plutonium was influenced by particle size. A general rule was proposed relating the size of particles and their behavior in RES organs. The whole-body autoradiographic technique reveals characteristic distribution patterns at early stages following intraperitoneal or subcutaneous injection. The behavior of plutonium soon after administration is largely influenced by its particulate character rather than by its elemental (chemical) nature. The results obtained following inhalation of a plutonium nitrate aerosol showed no obvious translocation of plutonium to the liver, despite the water solubility of the nitrate form. The initial uniform distribution of inhaled plutonium changed to a nonuniform distribution after 3 months. The effectiveness of DTPA treatment was studied in experiments involving injection of premixed Ca-DTPA and plutonium, or successive injections of Ca-DTPA to plutonium-burdened mice. The effectiveness of treatment was influenced by the physico-chemical state of the plutonium as well as by biological factors. It was demonstrated by diffusion chamber techniques that the chelating action of Ca-DTPA on plutonium colloids depends largely on their degree of polymerization.