114 II. DIGESTION AND ABSORPTION OF FATS 



intravenous route, cholic acid could be shown to enter the peripheral cir- 

 culation. 



Some bile acids may be normally excreted by the kidney. 461 Friedman 

 and collaborators 575 reported that, while some bile acids continued to be 

 discharged into the blood stream from the liver after obstruction of the bile 

 duct of the rat, the levels of plasma bile acids were increased 5 times above 

 this basal level if bilateral nephrectomy was performed simultaneously 

 with duct ligation. Moreover, it has been well known that, in man, bile 

 acids are eliminated by the kidney in jaundice or after their injection in 

 large amounts. 576 Yamasaki and Miyashita 577 reported that urinary ex- 

 cretion of dehydrocholate by rabbits, after its administration, was markedly 

 increased when the liver was poisoned by carbon tetrachloride. Simul- 

 taneous administration of vitamin B 12 or methionine, together with the 

 dehydrocholate, reduced its excretion to a normal level. 



A slight destruction of bile acids may occur in the liver. 578 ' 579 Licht 580 

 noted that some decomposition of the bile acids was brought about by 

 intestinal bacteria. Berman et a/. 581 suggested that the oxidation of the 

 bile acids to keto acids may account for the loss of these compounds. 

 However, the main pathway for loss is via the intestine, a fact which was 

 proved by Hoppe 582 and by Hoppe-Seyler 560 many years ago. Josephson 480 

 and Sobotka 467 agree that "since catabolic destruction of bile acids by the 

 animal organism is exceedingly doubtful, and since their elimination from 

 the body is almost entirely confined to the intestinal route, equilibrium is 

 maintained by synthesis of bile acids paralleling the rate of fecal losses." 

 Josephson 480 calculates that, in man, the bile salts are recirculated about 3 

 times before being broken down. The endogenous bile salt production of 

 bile fistula dogs has been found to be about 100 mg./kg./day. 571 



The mechanism of synthesis of the bile acids will be discussed in the sec- 

 tion on the intermediary metabolism of cholesterol in Volume III. It is of 

 interest to note here that Magee et «Z. 583 demonstrated the occurrence of a 

 mean daily increase of 25% in cholate production when the 10 essential 



576 M. Friedman, S. O. Byers, and F. Michaelis, Am. J. Physiol, 164, 786-788 (1951). 



576 S. S. Lichtman, Am. J. Physiol., 117, 665-671 (1936). 



577 K. Yamasaki and N. Miyashita, J. Biochem. (Japan), 39, 8 (1952). 



578 F. Rosenthal, L. Wislicki, and H. Pommernelle, Arch, exptl. Pathol. Pharmacol., 

 122, 159-183 (1927). 



579 J. Bollman and F. Mann, Arch. Pathol., 16, 304 (1933). 



580 H. Licht, Biochem. Z., 153, 159-164 (1924). 



581 A. L. Berman, E. Snapp, A. C. Ivy, A. J. Atkinson, and V. S. Hough, Am. J. 

 Digestive Diseases, 7, 333-346 (1940). 



582 F. Hoppe, Arch. -path. Anat. Physiol. (Virchow's), 25, 181-183 (1862). 



™ D. F. Magee, K. S. Kim, and A. C. Ivv, Am. J. Physiol, 169, 317-325 (1952). 



