328 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



intestinal tract is also fragmentary. Presumably they are carried in the 

 lymph in a manner similar to that for carotene and vitamin A, although 

 this has not as yet been proved. The tocopherols are found in blood, in 

 which 75% consist of the a-type and the balance of other types of toco- 

 pherols. 510 According to Rosenberg, 51 fi the total blood tocopherol amounts 

 to 56 7 % in men and 64 7 % in women; the blood level can be increased 

 to 100 7 % by feeding tocopherol. Vitamin E occurs in the blood as the 

 free vitamin, even after esters are administered. Quaife and Dju 517 

 reported that the total tocopherol contained in the entire blood of a man 

 amounted to 64 mg., and in a woman to 45 mg. 



(4) Vitamins K 



a. The Absorption of the Vitamins K from the Gastrointestinal Tract. 

 Vitamin K is quite unique among the fat-soluble vitamins in that it is 

 synthesized by the intestinal bacteria. This is indeed a fortunate circum- 

 stance in view of the fact that this vitamin does not have the widespread 

 distribution in plant and animal tissues which characterizes the other fat- 

 soluble vitamins. 



The natural forms of vitamin K (vitamins Ki and K 2 ) are soluble only 

 in fats, by virtue of the property conferred on them by their long hydro- 

 carbon side chains. On the other hand, menadione (2-methyl-l,4-naph- 

 thoquinone), which has the highest vitamin K biopotency of any natural 

 or synthetic product, is considerably more soluble in water, since it does 

 not contain the long aliphatic side chain. It is therefore obvious that 

 factors which are of importance in the absorption of the natural vitamins 

 K may play a considerably less important role in the utilization of mena- 

 dione and of similar synthetic products. 



Although no enzymes are required in order to prepare the natural or 

 synthetic vitamins K for absorption, the presence of bile is a prerequisite. 

 It was shown early that rats, 518 chicks, 519 and dogs 520,521 exhibited such 

 manifestations of vitamin K deficiency as loss of blood coagulability and 

 a low prothrombin level when the bile ducts were ligated. Greaves and 

 Schmidt 518 noted that the symptoms of vitamin K deficiency in rats could 



616 H. R. Rosenberg, Chemistry and Physiology of the Vitamins, Intersoience, New 

 York -London, 1945, p. 456. 



617 M. L. Quaife and M. Y. Dju, J. Biol Chem., 180, 263-272 (1949). 



6,8 J. D. Greaves and C. L. A. Schmidt, Proc. Soc. Exptl. Biol. Med., 37, 43-45 (1937). 



519 H. Dam and J. Glavind, Acta Med. Scand., 96, 108-128 (1938). 



520 W. B. Hawkins and K. M. Brinkhous, ./. Exptl. Med., 68, 795-801 (1936). 



521 H. P. Smith, E. D. Warner, K. M. Brinkhous, and W. H. Seegers. ./. Exptl Med.. 

 67,911-920(1938) 



