DIGESTION AND ABSORPTION 757 



x'itaniiii K. AliiKiuist and Stokstad*^ demonstrated that egg-yolk contains 

 considerable amounts of the \'itamin \\hen the hens are given a ^'it.amin K- 

 rich diet. Rosenberg'*'* reported that cow's milk is fairly rich in vitamin 

 K when the cow has received adecjuate amounts of the vitamin in her 

 rations. 



3. The Digestion and Absorption of the Vitamins K 



Vitamin K is available for absorption from the gastrointestinal tract 

 from two sources, namely that present in the diet and that synthesized 

 in situ. The natural forms of vitamin K are insoluble in water, and are 

 soluble only in fats, by virtue of the property conferred upon them as a 

 result of the long aliphatic side chains. However, menadione (2-methyl- 

 1,4-naphthoqiunone), which is the most potent compound with vitamin K 

 activity, is slightly soluble in water; it does not possess the aliphatic side 

 chain. It is therefore e^'ident that the factors in^'olved in the absorption 

 of the natural forms of vitamin K differ considerably from those of impor- 

 tance in the menadione absorption. 



No enzymes are rerjuired to prepare either the natural or the synthetic 

 K vitamins for absorption. However, as in the case of the other fat- 

 soluble vitamins and of fat itself, bile is essential to insure the absorption 

 of the vitamins K. Greaves and Schmidt^^ were the first to prove that 

 bile is necessary to enable rats to utilize vitamin K satisfactorily. The 

 importance of bile in the absorption of the vitamin has also been demon- 

 strated in chicks"^ and in dogs.^"'^' Manifestations of vitamin K deficiency 

 such as loss of coagulability of the blood, which was associated with a low 

 prothrombin content, occurred when the bile duct was ligated. It was 

 observed that the symptoms of vitamin K deficiency in rats with occluded 

 bile ducts could be partially relieved when vitamin K was given orally. 

 However, efficient recovery took place only when bile or bile salts were 

 administered along with the vitamin. According to Quick, ^^ bile salts have 

 the same relationship to the prothrombin level as to vitamin K. 



Schmidt^'- suggested that desoxycholic acid is responsible for bringing 

 about the absorption of vitamin K from the gut. Almquist and Klose^^ 

 reported the preparation of a vitamin K-choleic acid coordination complex 



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

 «> W. B. Hawkins and K. M. Brinkhous, J. Exptl. Med., 63, 795-801 (1936). 

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

 (57,911-920(1938). 



«2 C. L. A. Schmidt, Pacific Coast Med., 6, No. 3, 7-10 (1938). 



«3 H. J. Almquist and A. A. Klose. /. Am. Chem. Soc, 61, 745-746 (1939). 



