70 CHOLINE 



Little is known of the details of the synthesis of^ lecithin, for instance, 

 in the animal organism. In an attempt to clarify certain aspects of this 

 problem, Tolbert andOkey^^ injected P'Mabeled phosphate and C'*-methyl- 

 labeled choline simultaneously in rats and determined the specific activity 

 of various liver fractions after time intervals ranging from 3 to 96 hours. 

 Similar renewal rates for phospholipid choline and phospholipid phosphate 

 seemed likely because of the similarity in the rates of decrease in the spe- 

 cific activities of the two labeled fractions after reaching their initial maxi- 

 mum concentrations. Glycerophosphate satisfied the criteria for an imme- 

 diate precursor of phospholipid. 



Artom has investigated thoroughly the effect of choline and of related 

 compounds on the phospholipid content of livers of rats 2 to 3 months old 

 and fed diets low in protein and in sources of labile methyl. Significant 

 decreases were found in the total and in the choline-containing phospho- 

 lipids.^^ These decreases were only partly prevented by supplements of 

 choline administered at the start of the experiment and not prevented at 

 all if fatty infiltration was allowed to exist for 7 or more days prior to the 

 addition of choline to the diet." The absence of an effect of choline in the 

 latter experiments was not prevented by simultaneous administration of 

 various vitamins and amino acids, including methionine. In the case of 

 diets varying in fat content, the addition of choline after the development 

 of the fatty liver did restore the phospholipid level if 20 % or more of fat 

 was present in the ration.** Choline was more effective also if lactose re- 

 placed dietary sucrose.*^ The phospholipid turnover in intestinal mucosa 

 after the injection of P^- and the feeding of choline with and without fat 

 was less if the choline and fat were administered separately.®" The conclu- 

 sion seemed clear that choline increased phospholipid formation in the 

 intestine and did so especially during the digestion and absorption of fat. 

 Liver phospholipids were affected similarly.®^ Aminoethanol and mono- 

 methyl- and dimethylaminoethanol stimulated the formation of total 

 phospholipids in both intestine and liver as much as did choline. The 

 increase with choline was limited to the choline-containing phospholipids, 

 whereas both choline-containing and non-choline-containing phospholipids 

 were increased by aminoethanol and by its methylated forms. ®^ 



Artom 's demonstration of the inadequacy of choline for the complete 



" M. E. Tolbert and R. Okey, J. Biol. Chem. 194, 755 (1952). 



66 C. Artom and W. H. Fishman, J. Biol. Chem. 148, 405, 415, 423 (1943). 



"W. H. Fishman and C. Artom, J. Biol. Chem. 154, 117 (1941). 



58 W. H. Fishman and C. Artom, J. Biol. Chem. 164, 307 (1946). 



" C. Artom and W. H. Fishman, J. Biol. Chem. 170, 587 (1947). 



60 C. Artom and W. E. Cornatzer, J. Biol. Chem. 165, 393 (1946). 



61 C. Artom and W. E. Cornatzer, /. Biol. Chem. 171, 779 (1947). 



62 C. Artom and W. E. Cornatzer, J. Biol. Chem. 176, 949 (1948). 



