PHYSTOLOGIC ROLE OF VITAMIN K 761 



excreted in the urine. Altlioiifih the results on the pathway of alisorption 

 are convincing for the natural forms of vitamin K, they do not furnish 

 information conc(>rnin<i; the synthetic water-soluble forms such as mena- 

 dione. It would appear highly probable that a portion if not all of such 

 simpler preparations might be transported from the gut by the portal route 

 in the blood stream. Solvonuk et al.^^-^- found that, when labeled mena- 

 dione was injected intramuscularly into mice and cholecystonephrosto- 

 mized dogs, the material disappeared from the injection site, and that only 

 traces of radioactivity were found in the blood; 60% of the injected amount 

 was excreted in the urine within three hours. On the other hand, when 

 Dam and co-workers^^ injected vitamin Ki intravenously into chicks, they 

 found that it disappeared from the blood stream, and was deposited in the 

 liver, spleen, and lungs. No vitamin Ki could be detected in the bile. 

 After massive doses of vitamin Ki were injected, 16% could still be recovered 

 in the liver plus spleen after forty-two days. Apparently it is possible for 

 the tissues to store considerable amounts of vitamin K under some condi- 

 tions. 



Richert^^ reported that 4-amino-2-methvl-l-naphthol, 2-methyl-l,4- 

 naphthohydroquinone diphosphate, and 2-methyl-l-tetralone, which are 

 all powerful antihemorrhagic agents, are extensively converted to methyl- 

 naphthoquinone in the organism, and are excreted in combined form in the 

 urine. 



6. The Physiologic Role of Vitamin K 



(/) The Importance in Blood Coagulation 



The discovery of vitamin K and, in fact, most of the information con- 

 cerning this vitamin, have been based upon its requirement in the mainte- 

 nance of a normal blood-clotting mechanism. When vitamin K is withheld 

 from the diet, and when that synthesized in the gut cannot be absorbed, 

 an immediate and precipitous drop occurs in the prothrombin level in the 

 blood. It is evident that vitamin K in some way controls the synthesis of 

 this lilood protein, which is necessary in the clotting mechanism as a source 

 of thrombin. Hypoprothrombinemia is the immediate result of its absence 

 from the body. 



" P. F. Solvomik, L. B. Jaques, J. E. Teddy, T.. W. Trevoy, and J. W. T. Spinks, 

 Proc. Soc. Expll. Biol. Med., 79, 597-604 (1952). 



92 P. F. Solvonuk, J. M. Pepper, and G. J. Millar, Rev. can. hiol, 11, 83 (1952). 



9' H. l^am, I. Prango, and E. S0ndergaard, Acta pharmacol. et toxical., 10, 58-68 

 (1954). 



" D. A. Richert, J. Biol. Chem., 154, 1-8 (1944). 



