IV. BIOCHEMICAL SYSTEMS 505 



fed. As mentioned earlier,"'- vitamin E increased the utilization of vitamin 

 A in chicks, and the administration of 1 g. of tocopherol per day to New 

 Zealand cows raised the levels of carotene and vitamin A in their milk 

 fat/^ This sparing effect must be taken into account in any assessment of 

 the vitamin A value of a diet/"*' *^ 



These facts and the ineffectiveness of the acetate ester, previously ob- 

 served^' • ^^ and later confirmed,''^ suggested an antioxygenic action of tocoph- 

 erols in and near the alimentary tract rather than in the liver .''^ Such limi- 

 tation on the site of action of tocopherols does not explain the effectiveness 

 of otherwise suboptimal quantities of essential fatty acids in preventing 

 the fatty acid deficiency syndrome in rats when they receive tocopherol,''^ 

 which has not been confirmed,^" or the increased stability of tissue fats. 



This sparing action of tocopherols is definite, and the conflicting results 

 are doubtless due to uncontrolled variables, including the form and amounts 

 of \'itamins A and E administered,^^' ^^ the manner in which they are 

 given, °^' '"^ and the presence of inositol^^ or of stabilizers such as cephalin^® 

 or xanthophyll." 



The biological implications of this point of view were recently emphasized 

 by Dam and his colleagues, ^**-^'' who found that methylene blue, thiodi- 

 phenylamine, and Antabuse (tetraethylthiuram disulfide), when added to 

 vitamin E-deficient diets containing cod liver oil, caused an increased deip- 

 osition of vitamin A in the livers of chicks. The first two substances d d 

 the same in rats. When cod liver oil was replaced by lard, or when the diet 

 contained no fat, methylene blue had no effect on the vitamin A storage. 



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6» L. Anisfeld, S. M. Greenberg, and H. J. Deuel, Jr., /. Nutrition 45, 599 (1951). 

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