ROLE OF BILE IN LIQUID ABSORPTION 80 



that the same enzymatic mechanism mediates both syntheses. The 

 diminished excretion of hippuric acid observed in the Quick test after 

 benzoate is given to individuals having parenchymatous liver disorders is 

 believed to result from a failure in the glycine supply rather than from an 

 impediment in the enzymatic mechanism. Similar reasoning would apply 

 to the appearance of free cholic acid in the bile after the administration of 

 large doses of free cholic acid. 



The distribution of acids and related derivates in the bile of different 

 species of animals, as well as the component used in conjugation, are sum- 

 marized in Table 8 (page 80). Tables 9 and 10, on pages 83 and 84, give 

 data on the composition of the bile of teleost fishes. 



c. Properties of the Bile Acids. The bile acids are found under natural 

 conditions largely in the conjugated form. They occur as water-soluble 

 acids in which the carboxyl of the steroid acid is combined in peptide link- 

 age with either glycine or taurine. The greatest variations in properties 

 are to be found in the non-conjugated (nitrogen-free) acids obtained by hy- 

 drolysis of the conjugated compounds. 



The ring systems, as is evident from the structural formulas already 

 presented, are characteristic of the steroids. The configuration at C 5 is 

 similar to that in coprostanol (A/B = cm) while the rest of the molecule 

 corresponds to the natural sterols. 



One important reaction of the nitrogen-free bile acids is their tendency 

 to lose water when heated in a vacuum. The alcoholic groups are re- 

 moved, unsaturated acids are formed, all of which are convertible to the 

 same saturated cholanic acid on hydrogenation (6). 



Lithocholic acid ~ H '° ) Cholenic acid + 2 > Cholanic acid 



(3-Hydroxy- 

 cholanic acid) 



Desoxycholic acid ~ 2H '° ) Choladienic acids +2H \ Cholanic acid 



(3,12-Dihydroxy- 

 cholanic acid) 



Chenodesoxycholic acid ~ 2H2 ° > Choladienic acids +2 * > Cholanic acid 



(3,7-Dihydroxy- 

 cholanic acid) 



Cholic acid ~ 3H '° ) Cholatrienic acids +3 ' ) Cholanic acid 



(3,7.12-Trihydroxy- 



cholanic acid) 



Conversion of Bile Acids to Cholanic Acid (0) 



