DIGESTION, ETC. OP FAT-SOLUBLE VITAMINS 327 



et a/. 510 on human subjects. After 500 mg. of d-a-tocopherol were fed, 

 the maximum level of the serum tocopherol amounted to 1.75 mg. per 100 

 ml.; this maximum was reached in about four hours. After the ad- 

 ministration of a similarly large dose of rf-7-tocopherol, the peak value 

 was obtained in the serum after about the same time interval, but the 

 figure amounted to only 1 .35 mg. per 100 ml. of serum. 



Cows and hens have likewise been shown to exhibit a preferential ab- 

 sorption of a-tocopherol over 7- and 5-tocopherols. Cow milk is an ex- 

 ceedingly poor source of vitamin E. According to Abderhalden, 511 the 

 average tocopherol content of milk is only 0.001 milligram per cent. 

 Quaife and her eo- workers 510 were able to demonstrate a considerable rise 

 in the milk tocopherol value when the diet of the cow was supplemented 

 with ^-tocopherol. On the other hand, when the supplement was com- 

 posed of a mixture containing 00% of 7- and 5-tocopherols, the increase 

 in milk tocopherol was much less pronounced. 



In the case of chickens, the most sensitive index of the efficiency of 

 tocopherol absorption is to be found in the quantity of this vitamin in the 

 egg. 512 When a-, 7-, or 5-tocopherols were administered to hens in doses 

 of 100 to 4000 mg. per week, 510 ' 513 the tocopherol content of the eggs in- 

 creased linearly with the dosage. However, the storage of a-tocopherol 

 in the egg was much greater than was that after the administration of 7- 

 or 5-tocopherols. Thus, when the a-, 7-, or 5-tocopherol was fed at a 400 

 mg. level weekly, the concentration of tocopherols was 24.2, 5.7, and 2.3 

 mg. per 100 g. of the fresh egg, respectively. The relative efficiency of 

 transfer was 22.1% for a-tocopherol, compared with figures of 3.6% and 

 2.0% for 7- and 5-tocopherols, respectively. 



Bile is required for the absorption of the tocopherols, just as it is for 

 carotene, vitamin A, vitamin D, and for the fats. Greaves and Schmidt 514 

 reported that vitamin E was not absorbed when administered to the 

 choledochocolostomized rat. Moreover, dogs with bile fistulas have 

 likewise been shown to be incapable of absorbing this vitamin. 515 It is 

 not known whether the bile acids form coordination compounds with the 

 tocopherols or, if not, how they mediate their absorption. 



Information as to the transport of the tocopherols from the gastro- 



510 M. L. Quaife, W. J. Swanson, M. Y. Dju, and P. L. Harris, Ann. New York Acad. 

 Sci.,52, 300-305(1949). 



611 R. Abderhalden, Biochem. Z., 318, 47-53 (1948). 



512 G. L. Barnum, J. Nutrition, 9, 621-635 (1935). 



513 M. Y. Diu. M. L. Quaife, and P. L. Harris, .4m. J. Physiol, 160, 259-263 (1950). 



514 J. D. Greaves and C. L. A. Schmidt, Pror. Soc. Exptl. Biol. Med., 37, 40-42 (1937). 



515 K. M. Brinkhous and E. D. Warner, Am. J. Pathol, 17, 81-86 (1941). 



