TOCOPHEROLS IN VARIOUS METABOLIC PROCESSES 709 



normal. Koch^^° likewise noted that the injection of a-tocopherol caused 

 some increase in the liv^er glycogen of normal rats. 



c. Lipid Metabolism. The interrelations between dietary fat and the 

 tocopherols have been most widely recognized. The tocopherols originate 

 in plants; they are concentrated primarily in the plant lipids, where 

 they serve as fat antioxidants. In animals, the tocopherols, obtained from 

 dietary sources, are distributed to all fat depots, as well as to cell cyto- 

 plasmic lipids; here again they function as antioxidants. However, it 

 is not certain that this is their only function in the cells. 



The tocopherols function widely as antioxidants of fat, not only in vivo 

 but also in vitro. They protect the body from substances susceptible to 

 oxidation from which harmful products may originate. Just how the 

 tocopherols bring about this protection is a moot question. Tappel and 

 associates'''^ suggest the possibihty that antioxidants act by preventing a 

 biradical formation. The hypothesis that they provide a mechanism to 

 interrupt a chain reaction is also an attractive one. 



Although the antioxidant activity of the tocopherols is widespread in 

 reactions both in vitro and in vivo, there are certain types of in vitro effects 

 which Tappel'^^"'^^ and Hove'^^ independently concluded are more com- 

 parable to the in vivo changes under the specific control and regulation of 

 vitamin E. Thus, the autoxidation of unsaturated fatty acids is inhibited 

 by tocopheroV^ but to only a small extent by methylene blue.^^-^'^*'''^^ 

 In this case, tocopherol does not behave in vitro as it does in vivo. When 

 the oxidation of oleic acid is catalyzed by cytochrome c, it can be counter- 

 acted not only by tocopherol but also by methylene blue. Thus, both of 

 these antioxidants possess vitamin E biopotency. As an example of this 

 behavior, Lea'" demonstrated that the brown discolored fat, which is high 

 in hemoglobin, in pigs fed diets of whale oil, can be protected from this 

 accompanying peroxidation and from the oxidized odor by a-tocopherol, 

 despite an increased deposition of unsaturated fatty acids in the adipose 

 tissue. 



The interrelationship between the intake of rancid fats and the tocopherol 

 requirement has also been recognized for a long time. The rate of onset 



1'" R. Koch, Intern. Z. Vitaminforsch., 24, 68-75 (1952). 



>" A. L. Tappel, P. D. Boyer, and W. O. Lundberg, /. Biol. Chmi., 199, 267-281 

 (1952). 



"2 A. L. Tappel, Food Research, 18, 500-573 (1953). 



'" A. L. Tappel, Arch. Biochem. Biophys., U, 378-395 (1953); J,7, 223-225 (1953). 



'" A. L. Tappel, Arch. Biochem. Biophys., 50, 473-485 (1954). 



1" A. L. Tappel, Arch. Biochem. Biophys., 54, 266-280 (1955). 



"6 E. L. Hove, J. Nutrition, 50, 361-371; 51, 609-622 (1953). 



'" C. H. Lea, Chemistry andlndustry, 1953, 1303-1309. 



