528 IX. CAROTENOIDS AND VITAMINS A 



vitamin A. Thus, it was found that the apparent potency of 0.1 ng. of 

 carotene was multiphed by 2 to 2.5, while the effect on a 4 /xg. dose was in- 

 creased by a factor of 1.25 to 1.5, and the response of rats to 40 ^g. was not 

 improved by tocopherol. In the case of vitamin A, the response to 1 fig. 

 of vitamin A was increased 1.5 to 2.0 times by the optimum dose of to- 

 copherol, but the apparent potency produced by 30 ng. was not improved 

 by the administration of tocopherol. ^^- 



When rats were fed 0.8 /xg./day of carotene, the following increases in 

 body weight occurred over a period of thirty -six days as a result of the ad- 

 dition of several supplements :^^^'^^^ without vitamin E, 2 g. ; with 0.15 

 mg. mixed tocopherols, 31 g. ; with an equal amount of pure a-tocopherol, 

 27 g. ; of pure /3-tocopherol, 30. g. ; and of pure 7-tocopherol, 30 g. ; with 

 0.1 mg. pure ascorbic acid (vitamin C), 7.5 g. ; with 1 mg. ascorbic acid, 

 11 g. ; with 10 mg. ascorbic acid, 20 g. ; with 0.13 mg. hydroquinone, 3.3 

 g. ; with 35 mg. lauryl hydroquinone, 27.9 g. ; and with 0.5 mg. palmityl- 

 ascorbic acid, 30 g. 



There are several explanations for the beneficial effect of the tocopherols 

 on the utilization of vitamin A. Dubouloz et a/.^" and Quackenbush and 

 co-workers''"- were of the opinion that the tocopherols act as antioxidants 

 in the gastrointestinal tract, thus protecting the vitamin A from destruc- 

 tion. On the other hand, Hickman and co-workers^^^'''°'' and Harris et 

 aV^ noted that the tocopherols enhanced the growth produced by vitamin 

 A alcohol, by vitamin A acetate, and by standard U.S. P. reference oil. 

 Depletion of vitamin A was found to be more difficult if tocopherols were 

 given, while animals lived longer after the cessation of \'itamin A supple- 

 mentation if tocopherols were administered. ^°° These workers suggested 

 that tocopherols act synergistically with carotene and vitamin A. How- 

 ever, it was likewise indicated that the intestine is probably the site of ac- 

 tion of the tocopherols, inasmuch as the effect was greatly diminished when 

 the supplements of vitamins A and E were given on alternate days, as com- 

 pared with the results when they were given together.^'*- 



Lemley et al?^^ described the beneficial effect exerted by tocopherol, in 

 daily doses of 0.3 mg., on the liver storage of vitamin A when 100 I.U. of 

 vitamin A were given ; the effect was much less pronounced when the dose 

 of vitamin A was doubled. On the other hand, Guerrant,^''^ in a single 

 test, was unable to demonstrate any increase in storage of vitamin A in the 

 liver when an additional supplement of 3 mg. of a-tocopherol was added to 



'"2 F. W. Quackenbush, P. R. Cox, and H. Steenbock, /. Biol. Chem., 145, 169-177 

 (1942). 



'03 J. M. Lemley, R. A. BrowTi, O. D. Bird, and A. D. Emmett, /. Nutrition, 34, 205- 

 218 (1947). 



