28 METABOLISM IN THE NORMAL FUNCTIONAL STATE 



(Strickland, 1952; Johnson and Albert, 1953; Vladimirov, 1953; 

 Lissovskaya, 1954). Within 3 or 4 hr the specific radioactivity 

 reaches values of 0-3-0-5 of the specific radioactivity of the acid- 

 soluble phosphorus (Vladimirov et al., 1956; Johnson and Albert, 

 1954). The time course of incorporation into this and other 

 phosphates was studied by Strickland (1952). Radioactivity of 



8 

 Days after injection 



12 



Fig. 5. The incorporation of radioactive phosphorus into the 

 cerebral phosphates remaining after removal of the acid-soluble 

 and lipid phosphorus. Data from Strickland (1952). Cat, phos- 

 phate administered by intracisternal injection. • == phospho- 

 protein fraction; x = ribonucleic acid; O = residual organic 

 phosphorus; D = desoxyribonucleic acid. 



phosphoprotein phosphorus reached equilibrium with the in- 

 organic phosphorus of the brain within 6 days (Fig. 5) and a 

 relative specific activity of 0-5 within 6-12 hr. The initial rate of 

 exchange in this fraction is comparable with that in cephalin 

 diphosphoinositide (Fig. 4). The phosphoprotein fraction is not 

 homogeneous with respect to phosphorus exchange. Two phos- 

 phoprotein fractions have been found in guinea pig brain (Heald, 

 1959), one soluble in isotonic sucrose, the other attached to 

 particulate matter. In vivo radioactive phosphate injected intra- 

 cisternally was incorporated to a greater extent into the soluble 



