Originally publishod in Acta I'hy-siol. Scand. 3, 123 (1942). 



56. POTASSIUM INTERCHANGE IN 

 THE HUMAN BODY 



G. Hevesy 



From the Institute of Theoretical Physics, University of Copenhagen 



Interchange between the potassium present in the cells and the potas- 

 sium present in the extracellular fluifl of animals, can be determined by 

 using radiopotassium (*"K) as an indicator. Two methods were applied. 

 One method is based on the comparison of the ^-K content of the plasma 

 (extracellular) potassium and the ^-K content of the tissue potassium. 

 (Hahx et al., 1939, 1941; Fenn et al., 1941. Comp. also Joseph 

 ef ciL, 1939.) 



The other method (Hahn et al., 1939, 1941) is based on the measure- 

 ment of the amount of labelled potassium which disappeared in the 

 course of the experiment from the plasma. Since the amount of potassium 

 present in the tissue cells is many times larger than the amount of potas- 

 sium present in the extracellular space, a rapid interchange between 

 plasma (extracellular) potassium and cellular potassium will soon lead 

 to a strong depletion of the plasma ^^K content. The rate of disappearance 

 of 42j^ from the plasma (extracellular space) is, therefore, a very sensitive 

 measure of the rate of interaction between plasma (extracellular) potas- 

 sium and cellular potassium. This method has the disadvantage that 

 assumptions have to be made concerning the potassium content of 

 the tissue cells. The advantage of the method is its great simplicity. 

 It suffices to analyse the plasma or, as we shall see below, the urine. 

 In experiments on human subjects clearly the last mentioned alone 

 can be applied. 



EXPERIMENTAL PROCEDURE 



The labelled potassium was prepared by bombarding 80 mgm Iv(T 

 with a deuterium beam in the Copenhagen cyclotron. The activity obtain- 

 ed was 1/500 milliCurie. We are much indebted to Professor J. U. 

 Jacobsen and Mr. O. N. Lassen for preparing the radiopotassium. 

 The sample obtained was purified and dissolved in 20 cc. water. It was 

 taken 5 hours after the last meal by mouth by a male suljject weighing 



