THE NATURE OF BLOOD LIPIDS 353 



plasma. In the case of beef plasma, in harmony with the values of 

 Schaible, 16 the iodine value of phospholipid fatty acids 18,19 is about 71; 

 the average figure reported for pigs 18 was 80, while slightly higher values 

 were obtained for dogs, 18 ' 19 namely 89 and 97. 



Table 1 



Comparative Fatty Acid Composition of Various Fractions of Acetone-Soluble 



Plasma Lipids of Cow Blood" 



Free Glyceride Cholesterol 



fatty fatty ester 



Acids acids acids fatty acids Total 



Total weight, g 11.64 9.88 26.86 48.38 



Percent 24.1 20.1 55.5 100.0 



Fatty acid composition, mole per 

 cent 



Myristic 0.8 0.2 0.3 



Palmitic 34.4 33.7 11.1 21.4 



Stearic 5.2 22.2 3.3 7.6 



Arachidic 2.7 0.5 0.3 0.8 



Palmitoleic — 2.6 4.2 2.8 



Oleic 40.5 21.3 7.9 18.5 



Linoleic 16.4 18.4 61.7 42.1 



Linolenic — 9.2 5.0 



Arachidonic — 1.1 2.3 1.5 



Total saturated 43.1 56.6 14.7 30.1 



Total unsaturated 56.9 43.4 85.3 69.9 



° Adapted from F. E. Kelsey and H. E. Longenecker, /. Biol. Chem., 139, 727-740 

 (1941). 



Although the differences in iodine value may be a function of species, this 

 figure may also be related to the nature of the predominant food fat. 

 Sinclair 21 was able to demonstrate the incorporation of definite amounts 

 of elaidic acid in the plasma phospholipids of cats within a few hours after 

 this unnatural fat was fed. After several days of continuous feeding with 

 trielaidin, the elaidic acid content of the fatty acids of plasma phospholipids 

 amounted to as much as 37% of the total; however, since no elaidic acid 

 could be detected in the phospholipids of the red blood cells, it was con- 

 cluded that the erythrocytes do not participate in phospholipid transport. 

 If a similar behavior were noted in the case of phospholipids containing the 

 fatty acids ordinarily present, this would constitute strong evidence that the 

 cell phospholipid does not participate in phospholipid transport. 



b. Fatty Acids in Cholesterol Esters. For some time it has been recog- 

 nized that the most highly unsaturated fatty acids in the blood are present 



21 R. G. Sinclair, J. Biol. Chem, 115, 211-220 (1936;. 



