410 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



Table 1 

 Fractionation Data on Normal Animal Tissue"-'" 



" Data, for which the extreme values in each series are given, are expressed as per- 

 centages of the total phosphoHpid except where indicated otherwise. C = cephahn, L = 

 lecithin. 



k E. A. Welch, /. Biol. Chem., 161,65-69 (1945), p. 68. 



' Expressed as percentage of lecithin or cephalin sample. 



Taiirog, Entenman, and Chaikoff^^ have found that the phosphohpids 

 of the blood plasma of dog and man consist almost entirely of choline- 

 containing substances (lecithin and sphingomyelin). Only 5% or less of 

 the total phospholipid failed to contain choline. The low values for ceph- 

 alin in human plasma were substantiated by Hack,^^ while Sinclair^" 

 reports that the cephalin content of dog, beef, and pig serum, and of human 

 plasma, varied between 3 and 8% of the total phospholipids. However, 

 cephalin was shown to comprise 20% of the total phospholipids in turkey 

 sera {Meleagris gallopavo) . 



The low values for cephalin in plasma recently reported are at variance 

 with earlier figures found in the literature. These vary from 42%^^ to 

 30-20%"^-''^ of the total phospholipid. Chaikoff et aU^ attribute the 

 above discrepancies to inadequate analytical technics. These difficulties 

 have been overcome by a new procedure'*^ which involves adsorption of the 

 mixture on magnesium oxide. Under these conditions the non-choline 

 fraction is retained, and the choline-containing compounds are eluted. 

 The sphingomyelin content of plasma has been reported as 11%,*^ 17%,*" 

 and 19%*^ of the total plasma phospholipid, while Sinclair*" has stated that 

 sphingomyelin comprises 15 to 32% of the total phospholipid in human 

 plasma. 



38 A. Taurog, C. Entenman, and I. L. Chaikoff, /. Biol. Chem., 156, 385-391 (1944) 



39 M. H. Hack, J. Biol. Chem., 169, 137-143 (1947). 

 « R. G. Sinclair, J. Biol. Chem., 174, 343-353 (1948). 



" S, J. Thannhauser, J. Benotti, and H. Reinstein, /. Biol. Chem., 129, 709-716 

 (1929). 



" B. N. Erickson, I. Avrin, E. M. Teague, and H. H. Williams, J. Biol. Chem., 135, 

 671-684 (1940). 



" C. Artom, /. Biol. Chem., 139, 65-70 (1941). 



<* G. Brante, Biochem.^Z., 305, 136-144 (1940). 



« G. Blix, Biochem. Z., 305, 129-135 (1940). 



« A. D. Marenzi and C. E. Cardini, ./. Biol. Chem., 147, 371-378 (1943). 



« A. Taurog, C. Entenman, B. A. Fries, and I. L. Chaikoff, /. Biol. Chem., 155, 19-25 

 (1944). 



