This study was designed to compare the translocation from lung of the Pu contained in the pure and mixed industrial oxides PuO2 and (U,Pu)O2. The latter had a Pu content of 20% w/w. For this purpose, young adult male rats and male and female baboons were exposed to a single inhalation of these oxides. Two baboons were exposed to the reference PuO2, i.e. 239PuO2. Rats were killed under anaesthesia 1, 15, 30, 90 and 180 days after exposure, and baboons, also under anaesthesia, 1 year thereafter. The results indicate that lung retention of Pu was independent of the oxide inhaled, but was smaller in rat (12-15% of the initial pulmonary burden, 6 months after exposure) than in baboon (56-80% of this burden, 1 year after exposure). In rat, Pu translocation kinetics were similar for the two industrial oxides, but as from day 15 after inhalation until 6 months thereafter, measurement of Pu deposits in the liver and skeleton showed that translocation of Pu from the mixed oxide was 2-3 times greater than that from the industrial Pu oxide. In baboon, the largest amounts of Pu were retained in the lung and thoracic lymph nodes for the three oxides inhaled. Pu translocation to the liver, skeleton and kidneys, and also urinary Pu excretion, were greater after inhalation of the mixed oxide than after inhalation of the industrial and reference Pu oxides. Nevertheless, the amount of mixed oxide Pu translocated to these sites and excreted in urine remained under 3% of the initial pulmonary burden.
In vitro cellular dissolution tests for insoluble forms of uranium oxide are technically difficult with conventional methodology using adherent alveolar macrophages. The limited number of cells per flask and the slow dissolution rate in a large volume of nutritive medium are obvious restricting factors. Macrophages in suspension cannot be substituted because they represent different and poorly reproducible functional subtypes with regard to activation and enzyme secretion. Preliminary results on the dissolution of uranium oxide using immobilized alveolar macrophages are promising because large numbers of highly functional macrophages can be cultured in a limited volume. Cells were obtained by bronchoalveolar lavages performed on baboons (Papio papio) and then immobilized after the phagocytosis of uranium octoxide (U3O8) particles in alginate beads linked with Ca2+. The dissolution rate expressed as percentage of initial uranium content in cells was 0.039 +/- 0.016%/day for particles with a count median geometric diameter of 3.84 microns(sigma g = 1.84). A 2-fold increase in the dissolution rate was observed when the same number of particles was immobilized without macrophages. These results, obtained in vitro, suggest that the U3O8 preparation investigated should be assigned to inhalation class Y as recommended by the International Commission on Radiological Protection. Future experiments are intended to clarify this preliminary work and to examine the dissolution characteristics of other particles such as uranium dioxide. It is recommended that the dissolution rate should be measured over an interval of 3 weeks, which is compatible with the survival time of immobilized cells in culture and may reveal transformation states occurring with aging of the particles.
In vitro cellular dissolution tests for insoluble forms of uranium oxide are technically difficult with conventional methodology using adherent alveolar macrophages. The limited number of cells per flask and the slow dissolution rate in a large volume ofnutritive medium are obvious restricting factors. Macrophages in suspension cannot be substituted because they represent different and poorly reproducible functional subtypes with regard to activation and enzyme secretion. Preliminary results on the dissolution of uranium oxide using immobilized alveolar macrophages are promising because large numbers ofhighly functional macrophages can be cultured in a imited volume. Cells were obthned by bronchoalveolar lavages performed on baboons (AIpiop.qWo) and then immobilizd after the phagcytosis of uranium octoxide (U303) particles in alginate beads linked with Ca +. The dissolution rate expressed as percentage of initial uranium content in cells was 0.39 ± 0.016%/day for particles with a count median geometric diameter of3.84 Am(a3 = 1.84). A 2-fold increase in the dissolution rate was observed when the same number of particles was immobilized without macrophages. These results, obtained in vitro, suggest that the U30. preparation investigated should be assigned to inhalation class Y as recommended by the International Comnission on Radiolgicl Protection. Future experiments are intended to clarify this preliminary work and to examine the dissolution charaderisticsofother particles suchas uranium dioodde. It is recommended that the dissolution rate should be measured over an interval of 3 weeks, which is compatible with the survival time of immobilized cells in culture and may reveal transformation states occurring with aging of the particles. ICEA/DSV/DPTE/LRT, BP12-F-91680 Bruyeres le Chatel, France.
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