J.Jpn. Surg. Soc.. 58(12): 1956-1976, 1958

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STUDIES ON THE REMOVAL OF INTERNAL RADIOACTIVE CONTAMINATION

In recent years many authors have attempted to remove radioisotopes from the body by means of complexing agents. When the chelate is water-soluble ＆ readily diffusible, it is readily excreted. The chelating agent removes the radio-active metal ion from the combination with cellular constituents with subsequent elimination of the complexed radioactive metal from the body. Many investigators reported that of all the chelating agents EDTA was the most successful in removing rare earths ＆ transuranic elements. The authors made a survey of the effect of different uses of EDTA on the excretion of radioisotopes of the Bikini ash and mixed fission products in rabbits and mice. Hardly any differences were noted in these studies. Consequently, we had used Ca-EDTA in our experiments.
Radioactive metals in blood of mammalians will migrate primarily to the bone-beams and deposit gradually in the cortical tissue. Because it is difficult to remove metals which are already deposited into the cortical tissue, experimental study on removal of absorbed fission products was performed in an early stage. The following two-stage decontamination method was devised in rabbits by the authors, at first, mobilizing the fission product from the skeletal tissue to circulatory blood with Parathormon, then it would be more readily cleared from the blood to the urine with Ca-EDTA. Rabbits treated with Ca-EDTA, Parathormon or Parotin were regarded as the control group. 150-400 micro curie of mixed fission products was injected subcutaneously in rabbits. 3-5 days after injecrion of FP-1, injection of 1 gm. of 20% Ca-EDTA ＆ 100 u.s.p. of Parathormon per day was performed for 10 days. Radioactivity of urine in the treated group was 49.7%-63.2%, otherwise, that of the control group was 30.2%-34.9%. But remaining activity of the skeletal bone decreased to only about 18% from about 29% of control group. The method of decontamination mentioned above was more effective than the treatment with Ca-EDTA alone. In cases of Y⁹¹ injection, the effect of decontamination was much larger than in cases of mixed fission product injection. The treatment mentioned above had little effect when Sr⁸⁹ was injected. Decarcification therapy with Parathormon by the authors was not able to increase the decontaminating effects both in cases of mixed fission product injection and Sr⁸⁹ .
Thus, the method of decontamination with Parathormon and Ca-EDTA was regarded as a more effective method against some elements of the fission products, but the effect was not satisfactory in the permissible dose of these drugs. Each element of the fission products could be removed with some complex method, however, a series of "Bone Seekers" could hardly be decontaminated without harming the individuals affected.
(author's abstract)

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