90 II. DIGESTION AND ABSORPTION OF FATS 



When 3-hydroxy-12-ketocholanic acid was given parenterally to rabbits, 

 Mori 492 was able to isolate considerable amounts of desoxycholic acid 

 (3,12-dihydroxycholanic acid). Desoxycholic acid was likewise demon- 

 strated in the bile after the feeding of 3a-hydroxy-6-ketocholanic acid 493 ; 

 this unusual finding is explained by Tukamoto on the hypothesis that, 

 when foreign bile acids are fed, the normal pathways for conversion of the 

 bile acids are inhibited. 



(b) Removal of Hydroxyl Groups. Not only may the number of hydroxy 

 groups be decreased, along with a concomitant reduction in ketone groups, 

 but this may also occur in cholic acid (3,7,12-trihydroxycholanic acid) 

 from which ketone groups are absent. Thus, Kim 494 proved that, in the 

 case of guinea pigs, desoxycholic acid is excreted both in the bile and in the 

 urine after the administration of cholic acid. 



(c) Oxidation of Hydroxy- to Keto- Acids. Under certain conditions the 

 animal organism is able to bring about the reverse change to that illustrated 

 in (a), namely the oxidation of hydroxycholanic acids to the corresponding 

 keto acids. Sasaki 491 reported that, after the incubation of guinea pig 

 liver brei with cholic acid (3,7,12-trihydroxycholanic acid), he was able to 



OH CH 3 

 CH 3 

 /_ 



HjC 



COOH /\ /\/\/ COOH 



HO OH HO O 



Cholic Reductodehydrocholic 



acid acid 



COOH 



Dehydrocholic 

 acid 



Conversion of Cholic Acid and Reductodehydrocholic Acid 



to Dehydrocholic Acid in the Cuinea Pis (8) 



492 T. Mori, Z. physiol. Chem., 258, 143-146 (1939). 



493 M. Tukamoto, Z. -physiol Chem., 260, 210-216 (1939). 



494 C. H. Kim, Z. physiol. Chem., 261, 97-102 (1939). 



