Originally publishod in Kgl. Danske V ideu-shahevnes Selskah. Biologiske Meddeleher 



13, '.) (1037) 



19. STUDIES ON THE METABOLISM OF PHOSPHORUS 



IN ANIMALS 



O. Chievitz and Ci. Hevesy 

 From the Instituto of Theoretical Physics, University of Copenhagen 



In a recent letter to Nature^ we communicated the results of some 

 experiments on the metabolism of phosphorus using a radioactive 

 phosphorus isotope as indicator. What follows is a more detailed descrip- 

 tion of some of our experiments, carried out chiefly on rats but partly 

 also on human subjects. 



PRINCIPLE OF THE METHOD USED 



Disregarding hydrogen, the only element which is ever met with in 

 a nuclear state (as a proton) in chemical reactions, isotopes do not 

 separate to a measurable extent during chemical or biochemical processes. 

 It follows from this inseparability that Avhen a known amount of radio- 

 active phosphorus is added to, for example, 1 mgm of phosphorus 

 the presence of the former will always indicate the presence of the latter, 

 we can thus distinguish for example between the phosphorus atoms 

 taken in with the food (to which we add some radioactive phosphorus) 

 and those already present in the system. The use of isotopic indicators 

 is not dependent on an absolute inseparability of isotopes by chemical 

 methods. We know indeed that minute separations almost always 

 occur. It is sufficient that, within the analytical accuracy claimed, no 

 separation takes place. 



Phosphorus has only one stable isotope ^^P but we can prepare un- 

 stable radioactive isotopes of phosphorus having atomic weight of 

 150 and 32; the latter has a half-life of about a fortnight and is \ery 

 suitable for use as an indicator. It was used by us in many experiments 

 of different kinds. 



10. Chievitz and G. Hevehy, Nature 136, 754 (1935). 



