LIPID CONTENT AND COMPOSITION OF ANIMAL 595 



However, in the ewes as well as in the pigs, the variations brought about by 

 fasting were minor. 



There is some question as to whether or not a definite sparing action is 

 exerted upon the essential fatty acids during fasting. Chevallier et al. 33s 

 found that the amount of arachidonic acid in the organism of the rat re- 

 mained remarkably constant during fasting, despite a decrease in total 

 lipids. The constancy with which the concentration of tetraenoic acid is 

 maintained in the tissues during fasting does not appear to be shared by the 

 dienoic and trienoic acids. Thus, it was noted by Manuel and Chevallier 339 

 that the injection of thyroxine, which causes a decline in total lipids in the 

 organism, similar to that brought about by fasting, is followed by a de- 

 crease of the dienoic acids in the rat and guinea pig, and of trienoic acids in 

 the guinea pig. Little variation in the quantity of tetraenoic acid obtains 

 in these two species as a result of the injection of the thyroid hormone. On 

 the other hand, Evans 340 found that the absolute decrease in the fat content 

 of the bone-marrow of starved rabbits affected equally the polyunsaturated 

 fatty acids, oleic acid, and the saturated acids. 



When short-chain fatty acids are present in the depot fats at the start of 

 the fast, these are first oxidized. Channon et al. 31 were the first to demon- 

 strate that, after a diet containing 40% of coconut oil was fed for fourteen 

 and twenty-one days, respectively, the depot fat contained 0.9 and 1.2% of 

 capric acid, 7.8 and 17.2% of lauric acid, and 13.4 and 13.8% of myristic 

 acid. In the studies of Reed et al. 2b0 in the Yale laboratories, it was found 

 that the depot fat of rats, previously on a coconut oil diet, became more un- 

 saturated when the animals were subjected to fasting. It was suggested 

 that a relative increase in phospholipids during fasting might account for 

 the increased unsaturation which they observed. When the depot fats 

 consisted primarily of palmitic, oleic, and linoleic acids, no comparable 

 changes were observed during inanition. 51 ' 52 Longenecker 32 confirmed 

 these earlier results by an analytical demonstration of the rapid loss of the 

 saturated acids during fasting on the part of rats previously on a coconut 

 oil diet. The author considers that these results lend unqualified support 

 to the hypothesis that acids of lower molecular weight are preferentially 

 utilized. However, the increased rate of utilization of the Ci 2 to Cie acids 

 may be attributable to the fact that they are present in the glycerides in 

 maximum concentration (two molecules per triglyceride). Under these 



338 A. Chevallier, C. Burg, and R. Wagner, Compt. rend. soc. biol, 144, 1396-1397 

 (1950). 



339 S. Manuel and A. Chevallier, Compt. rend. soc. biol., 145, 1369-1371 (1951). 



340 J. D. Evans, Federation Proc, 12, 41 (1953). 



