[Application of thorium B labeled red corpuscles in blood volume studies].

THE SUCCESSFl'L application of radioactive indicators in physiology caused the early introduction of a radioactive component into the erythrocytes and their use in blood volume determinations. While this method has found application in animal experiments, it is not very suitable for determination of the blood volume of humans, since ironlabeled red corpuscles can only be obtained in vivo, and thus the application of this method depends on the availability of iron-labeled donors. On the other hand the use of P labeled red corpuscles has found a very extended application in blood volume determinations. This method necessitates incubation of the blood sample with radioactive phosphate for an appreciable time. It also requires centrifuging of blood samples and washing of red corpuscles, which consume much time. An ideal radioactive method of clinical blood volume determination should fulfill the following conditions: (a) The radioactive source should be available at a moment's notice, and should not need replacement for some years. (b) The rays emitted by the radioactive indicator should be easily measurable. (c) No significant loss of the radioactive indicator by the red corpuscles should take place in the circulation in the course of the experiment. (d) The half-life of the radioactive indicator should be sufficiently long, amounting to at least several minutes, to enable a trained nurse to carry out the radioactive measurements