SOURCES OF PAT IN ANIMAL BODY 529 



view of the fact that stearic acid can readily be synthesized in vivo from 

 carbohydrate (see page 538), it is obvious that the animal body is not 

 dependent upon the dietary oleic acid for supplying the needs of this 

 monoethenoid acid in tissue lipids. 



(b) Elaidic Acid. Elaidic acid, £rans-9,10-octadecenoic acid, is the 

 geometric isomer of oleic acid. Unlike the latter compound, elaidic acid 

 is never found normally in animal or vegetable fats. In contradistinction 

 to oleic acid and trioleins, which are liquids at ordinary temperatures, 

 elaidic acid and its triglyceride, trielaidin, are solids at room temperature, 

 although they melt at temperatures only slightly above that of the body, 

 i.e., at 43.7°C. and 42°C, respectively. The elaidinization reaction, 

 which is a reversible one in the laboratory, can readily be brought about by 

 the use of mercurous nitrate, nitrous acid, nitrous oxide, sulfurous acid 

 and selenium. For a further discussion of this reaction, see Volume I, 

 pages 85 and 86. 



In the case of the animal body, neither the process of elaidinization nor 

 the reverse reaction can be effected. Barbour 45 reported that "isooleic 

 acid," which is present in hydrogenated cottonseed oil, is deposited in the 

 adipose tissues of the rat, and is eventually utilized as fuel for the animal 

 body in a similar manner, and to the same extent, as are other dietary fatty 

 acids. Although the exact composition of the so-called isooleic acid is 

 uncertain, Barbour suggests that it consists largely of elaidic acid, also of 

 some A 12 - 13 -acid, resulting from the partial hydrogenation of linoleic acid, 

 as well as still other isomers of oleic acid. 



Sinclair 46 was the first to use pure elaidic acid and trielaidin for following 

 the intermediary fat metabolism. These compounds behaved in exactly 

 the same manner as normal fatty components. The course of the in- 

 termediary metabolism of elaidic acid could be followed, since its properties 

 allowed it to be readily differentiated from the other fatty acids. It was 

 found that, when elaidic acid was fed to normal growing rats, it made up 

 one-third of the total fatty acids in the phospholipids of the liver and 

 skeletal muscle. On the other hand, when it was administered to adult 

 rats on ordinary diets, elaidic acid was shown to replace 25 to 30% of the 

 natural fatty acids. The saturated acids were the ones largely replaced. 

 In later studies, McConnell and Sinclair 12 were able to demonstrate that 

 elaidic acid could be introduced to the extent of 30% into the lecithin and 

 cephalin fractions of the rat. Kohl 47 confirmed the fact that elaidic acid is 



45 A. D. Barbour, J. Biol. Chem., 101, 63-72 (1933). 



46 R. G. Sinclair, J. Biol. Chem., Ill, 515-526 (1935). 



47 M. F. F. Kohl, /. Biol. Chem., 126, 709-719 (1938). 



