DIGESTION, ETC. OF STEROLS IN THE G.I. TRACT 261 



sufficient to result in a minimum absorption of cholesterol from the gas- 

 trointestinal tract on a cholesterol-rich diet, a large excess of bile salts must 

 be furnished if appreciable amounts of cholesterol are to be deposited in 

 the liver. The rate of increase in blood and liver cholesterol in rats fed a 

 1% cholesterol diet with 0.5% bile salts is illustrated in the results of 

 Alfin-Slater el at? 1 which are summarized in Table 3 (page 262). 



Schonheimer 78 found that an optically visible lipemia could be produced 

 in rabbits by means of a single cholesterol feeding along with bile salts. 

 However, Member and his co-workers 79 were able to produce an increased 

 deposition of cholesterol in the aortas of rabbits, as a result of feeding this 

 sterol, only when cholic or glycocholic acid was fed concomitantly. The 

 cholesterol levels in the aorta were no higher than the controls when de- 

 hydrocholic, hyodesoxycholic, or desoxycholic acid was included in the diet. 

 A summary of these data is given in Table 4 (page 263). 



Finally, Siperstein, ChaikofT, and Reinhardt, 80 employing C 14 -labeled 

 cholesterol, concluded that bile plays an obligatory role in the passage of 

 cholesterol from the intestinal tract to the lymph. Although these 

 workers found that the absorption of palmitic acid was likewise increased 

 by the presence of bile, it was noted that small amounts of palmitic acid 

 can be absorbed when bile is completely eliminated from the gastroin- 

 testinal tract. 



The mechanism by which bile salts facilitate the absorption of cholesterol 

 is uncertain. However, Wieland and Sorge 81 found that cholesterol is 

 one of the substances which can be dissolved by the hydrotropic action of 

 sodium desoxycholate and other bile acids. Moreover, Downie et al. s2 

 reported a coordination compound in which cholesterol is the acholic 

 component. The best explanation for the absorption of cholesterol is 

 therefore the fact that it is rendered possible by the hydrotropic action 

 of bile salts, and that it is facilitated when cholesterol is dissolved in fat. 



(c) The Esterification of Cholesterol in Relation to Its Absorption. Peter- 

 son et a/. 76 demonstrated that phytosterols produce a depressive effect on 

 the absorption of cholesterol in chickens. It is suggested that this may 

 be due to inhibition exerted by the latter compounds on the cholesterol- 

 esterifying system in the intestinal mucosa. Since it is known that the 



77 R. Alfin-Slater, M. Schotz, S. M. Greenberg, and H. J. Deuel, Jr., unpublished 

 data, 1952. 



78 R. Schonheimer, Biochem. Z., U7, 258-263 (1924). 



79 S. Member, M. Bruger, and E. Oppenheim, Arch. Pathol, 38, 210-214 (1944). 



80 M. D. Siperstein, I. L. ChaikofT, and W. O. Reinhardt, J. Biol. Chem., 198, 111-114 

 (1952). 



81 II. Wieland and H. Sorge, Z. physiol. Chem., 97, 1-27 (1916). 



82 A. W. Downie, L. Stent, and S. M. White, Brit. J. Exptl. Pathol, 12, 1-9 (1931). 



