486 ADVENTURES IN RADIOISOTOPE RESEARCH 



ON THE ORIGIN OF PHOSPHATIDES OF PLASMA AND CORPUSCLES 



We have already mentioned that the amount of labelled phosphatides 

 formed in the blood within a few hours is entirely negligible compared 

 to that of labelled acid-soluble organic compounds formed. The phos- 

 phatides present in the plasma are released by the organs in which 

 phosphatides are synthesized, primarily by the liver, but also by the 

 intestinal mucosa, and possibly by other organs. The synthesis of phos- 

 phatides in the different organs was investigated in recent years using 

 fatty acids, which could be traced by chemical analysis -^\ and also by 

 the use of radioactive P as an indicator'^^) j^ several cases the change 

 in the degree of saturation of the fatty acid component of the phospha- 

 tides extracted from the intestinal mucosa, liver, etc., was studied after 

 feeding cod liver oil which contains a large amount of unsaturated fats. 

 Within a short time an increase in the iodine number of the fatty acids 

 was found. For example, within 2 days after the change of diet the 

 iodine number of phosphatides of the intestinal mucosa increased from 

 93 to 160. From this result it follows that within 2 days an appreciable 

 amount of the phosphatide molecules present in the intestinal mucosa 

 was renewed. Instead of feeding a mixture of fatty acids showing a 

 different degree of saturation and having a high average iodine number, 

 Sinclair, fed, in his later experiments, fats containing pure (85%) 

 elaidic acid, a geometric isomer of oleic acid, an easily traceable sub- 

 stance, since it forms a lead salt which is insoluble in ether, differing 

 in this regard from all other unsaturated acids. 8 hours after feeding 

 elaidic acid to cats, 15% of the fatty acids extracted from the plasma 

 phosphatides were found to contain elaidic acid, while hardly any was 

 found in the phosphatides obtained from the corpuscles. This result may 

 be possibly interpreted as a proof of lack of a phosphatide turnover in the 

 corpuscles. Another chemical indicator used to follow up the turnover of 

 phosphatides is iodised fat which was fed by Artom to animals. Also 

 in this case the presence of iodised fatty acid in the phosphatide molecule 

 is a proof of their formation after the administration of iodised fat. 

 By using this method Artom found the presence of iodised fatty acids 

 in the phosphatides extracted not only from the plasma but also from 

 the corpuscles. In the latter the concentration of the iodised fat was 



(i) Comp. R. G. Sinclair's Physiol. Bcr. 14, 351 (1934). The papers of the same 

 author and collaborators, J. Biochem. 115, 211 (1936); 118, 122 (1937): 121, 361 

 (1937): C. Aktom, Arch. int. Physiol. 36, 101 (1933). 



(2) C Artom, C. Perkier, M. Santangello, G. Sarzana anclE.SEGRE, Arch. 

 I7it. Physiol. 45, 32 (1937); 47, 245 (1938); L. Hahn and G. Hevesy, Skand. Arch. 

 Physiol. 77, 148 (1937); G. Hevesy and E. Lundsgaard, Nature 140, 275 (1937). 

 B. A. Fries, S. Ruben, I. Perlman and I. C. Chaikoff, J. Biol. Chem. 122, 

 169 (1937): 123, 587 (1938). 



