COMPARATIVE BIOPOTENCIES 797 



mitic acid, according to Stetten and Schoenheimer,^^ while a similar 

 desaturation of myristic acid was shoAvn to occur, resulting in the formation 

 of the monoethenoid acid, myristoleic acid, described by Anker.^^ 



In sharp contrast to the ease of synthesis of the monoethenoid acids 

 from the corresponding saturated fatty acids, Bernhard and Schoenheimer^^ 

 demonstrated that the rat is unable to synthesize either the diethenoid 

 acid, linoleic, or the triethenoid acid, linolenic, from carbohydrate, al- 

 though large amounts of stearic and palmitic acids were shown to originate 

 concomitantly from this foodstuff. Thus, saturated and monoethenoid 

 acids, which have most important functions in the animal, are considered 

 to he non-essential from a dietary standpoint, since they can be synthesized 

 oven on nonfat diets. On the other hand, linoleic, linolenic, and arachi- 

 donic acids are regarded as essential. 



The requirements of different animals for essential fatty acids differ 

 considerably. Since tissue lipids, especially phospholipids, invariably con- 

 tain significant amounts of EFA, one may conclude that some animals must 

 l)e able to synthesize the compounds, but that the degree of this ability 

 varies not onlj^ between ph34a class and species, but also between differ- 

 ent age groups within the same species. There is direct evidence of the 

 ability of adult animals to synthesize "essential" fatty acids. Barki and 

 associates'^ reported that the adult rat may not only recover from fatty 

 acid deficiency on a fat-free diet, but may even increase its content of lino- 

 leic, linolenic, and arachidonic acids. Reiser, Gibson, Carr, and Lamp*' 

 showed that hens on a fat-free ration for one year continued to lay eggs 

 containing appreciable quantities of linoleic acid. 



(5) The Question of the Possible Biopotency of Oleic Acid and of Other Mono- 

 ethenoid Acids 



Burr and Burr^ were originally of the opinion that oleic acid might possess 

 some activity in counteracting the fat-deficiency syndrome. Burr et 

 al^-^^ later reported that the monoethenoid acid was completely devoid of 

 bioactivity. Evans and Lepkovsky^" also reported the negative effect 

 of oleic acid in preventing fat deficiency. Moreover, it was recently (1954) 



85 De W. Stetten, Jr., and R. Schoenheimer, ./. Biol. Chem., 133, 329-.345 (1940). 

 8« H. S. Anker, J. Biol. Chem., 194, 177-182 (1952). 



"K. Bernhard and R. Schoenheimer, ./. Biol. Chem., 133, 707-712, 713-720 (1940). 

 8« V. H. Barki, R. A. CoUins, E. B. Hart, and C. A. Elvehjem, Proc. Soc. Exptl. Biol 

 .Wer/.,?7,(594-()9(i(1949). 



»» R. Reiser, B. Gibson, M. J. Carr, and B. G. Lamp, ./. Xutrition, 44, 159-17G (1951). 

 9» H. M. Evans and S. Lepkovsky, ./. Biol. Chem., 06, 157-164 (1932). 



