Originally puhlishod in Biochcm. J. 34, 532 (1940) 



21. RATE OF REJUVENATION OF THE SKELETON 



G. CH. Hevesy, II. B. Levi and O. II. Rebbe 

 From the Institute of Theoretical Physics, University of Copenhagen 



The first experiments in which labelled (radioactive) phosphorus ^-P 

 was applied as an indicator [Chievitz and Hevesy, 1935], showed 1 

 ihat some of the phosphorus atoms of the mineral constituents of tlu^ 

 hone exchange rapidly with Ihose present in the plasma. This result 

 was corroborated and extended by later work on this subject [Hevesy 

 et ah, 1937; Cook et al., 1937; Dols et al, 1937; 1939; Artom et al., 

 1938; (John and Greenberg, 1939; I^efevre and Bale, 1939]. The 

 question as to what extent the P contents of the mineral constituents 

 of the bone are replaced in a given time by plasma P remained unan- 

 swered however. This is an important question, as the rate of this repla- 

 cement is a measure of the rate of rejuvenation of bone tissue. The extent 

 to which bone P is replaced by plasma P in the course of a given time 

 can be determined by comparing the activity of 1 mgm of bone P with 

 that of 1 mgm of inorganic plasma P. The activity of the plasma P, i.e. 

 its 32P content, changes appreciably, however, with time. The ^-P atoms, 

 like all P atoms present at any moment in the plasma, exchange with 

 the P atoms present in the various organs and in doing so are removed 

 from the plasma and replaced by tissue P. The application of the above- 

 mentioned consideration implies a constancy of the activity of the plasma 

 inorganic P. To secure such a constancy, we administered labelled phos- 

 phate all through the experiment, instead of doing so at the start of th(> 

 experiment, as in all investigations mentioned above. By taking blood 

 samples at intervals, we ascertained that the activity of the inorganic 

 P of the plasma remained constant. At the end of the experiment, the 

 l^one sample Avas purified from all non-mineral constituents and Ili<' 

 radioactivity of 1 mgm of bone P compared with that ol" 1 mgm ol 

 plasma inorganic P. 



EXPERIMENTS WITH FROGS 



Experiments of 5 to 240 min duration wore carried out with frogs. As early 

 as 5 min after injecting 0.3 ml. physiological NaCl solution containing a negli- 

 gible proportion of labolkvl sodium phosphate into llio lymph sac, the minersil 



