Originally published in Scand. Arch. Physiol. 77, 148 (1937) 



27. THE FORMATION OF PHOSPHATIDES IN THE BRAIN 

 TISSUE OF ADULT ANIMALS 



L. Hahn and G. Hevesy 

 From the Institute of Theoretical Physics, University of Copenhagen 



It is generally assumed that no regeneration of the brain tissue of adull 

 animals takes place. To test the validity of this assumption we investi- 

 gated whether any formation of phosphatides takes place in the brain 

 tissue of adult animals. This problem cannot l)e attacked by ordinary 

 chemical methods because these do not permit the making of a distinction 

 between phosphatide molecules formed at different dates; this is, how- 

 ever, possible if we introduce a labelled phosphate into the animal body 

 (Chievitz and Hevesy, 1935, 1937), labelled sodium phosphate for 

 example, and investigate whether the formation of labelled phosphatides 

 can be established in the brain of the animal. We carried out experi- 

 ments on rats, mice^ and rabbits. 



Labelled phosphorus can be obtained by adding radioactive phos- 

 phorus to ''normal" phosphorus. If we dissolve for example 1000 rela- 

 tive (radioactive) units of the radioactive phosphorus isotope ^^P in a 

 solution containing 1 mgm of phosphorus, say as sodium phosphate, 

 and administer this solution to an animal, then the presence of 1 relative 

 radioactive unit in a part of the animal tissue will prove the presence 

 of ^/looo ^^ ^^^^ total number of phosphorus atoms administered. The 

 radioactive ^^P used in our experiments was obtained by bombarding 

 carbon disulphide with fast neutrons from a mixture of radium sulphate 

 and beryllium. 



Phosphatides are the second most al)undant constituents of the brain 

 tissue. The composition of the latter is shown in Table 1. 



Table 1. — Compositiox of the dky Brain 

 Tissue of Adilt Albino Rats 





Protein 



PliDsphatide.s 



Lipides not containing P 1 



.Kstei-s and inorganic constituents . . . 9.S 



48..-) 



2(i.r) 



