DIGESTION, ETC. OF STEROLS IN THE G.I. TRACT 259 



fact that an increased unsaponifiable fraction was noted in the liver oil 

 after this alcohol was fed. 



A u - 12 -Eicosenol and A 13 - 14 -docosenol, two unsaturated alcohols which 

 occur in the wax, jojoba oil, are partially digested by the rat. 22 For a dis- 

 cussion of the digestibility of these alcohols when fed as the esters, see 

 page 251. 



5. The Digestion, Absorption, and Transformations of Sterols in 

 the Gastrointestinal Tract 



(/) The Digestion and Absorption of Cholesterol 



a. Absorption Experiments with Cholesterol. The best proof of the ab- 

 sorption of cholesterol is afforded by the demonstration of increased 

 cholesterol in the blood, lymph, and tissues after this alcohol is fed. As 

 early as 1906, Pribram 55 reported an increase in the blood cholesterol of 

 rabbits following the ingestion of cholesterol as the free alcohol or as the 

 ester. 



Gardner and co-workers, 56-58 Lehman, 59 Knudson, 60 Ssokoloff, 61 and 

 Mjassnikov and Iljinsky 62 have all reported that the feeding of cholesterol 

 results in an increased level in the blood. According to Gardner el al., 

 56-58 tn e feeding of cholesterol either as the free alcohol or as the ester pro- 

 duces an augmentation of the blood cholesterol; however, it was shown 

 that the cholesterol esters are hydrolyzed before being absorbed. 



Mueller 63 - 64 found that the cholesterol content of chyle was increased 

 after the administration of this sterol; the proportion of free alcohol to 

 ester in the chyle was similar to the proportion in the blood. Moreover, 

 the amount of chyle cholesterol increased after the administration of this 

 substance in either the free or the ester form. These results are also in 

 line with the observation that a cholesterol esterase system is present in the 

 wall of the small intestine, and can bring about both hydrolysis and esteri- 

 fication. 65,66 



58 H. Pribram, Biochem. Z., 1, 413-424 (1906). 



66 C. Doree and J. A. Gardner, Proc. Roy. Soc. London, B81, 109-128 (1909). 



67 M. T. Fraser and J. A. Gardner, Proc. Roy. Soc. London, B81, 230-247 (1909). 



68 M. T. Fraser and J. A. Gardner, Proc. Roy. Soc. London, B82, 559-568 (1910). 



69 E. P. Lehman, J. Biol. Chem., 16, 495-503 (1914). 



60 A. Knudson, J. Biol. Chem., 45, 255-262 (1921). 



61 S. A. Ssokoloff, Z. ges. exptl. Med., 46, 650-655 (1925). 



62 A. Mjassnikov and B. Iljinsky, Z. ges. exptl. Med., 58, 100-106 (1926). 

 68 J. H. Mueller, J. Biol. Chem., 22, 1-9 (1915). 



64 J. H. Mueller, J. Biol. Chem., 27, 463-480 (1916). 



85 M. L. Nieft and H. J. Deuel, Jr., /. Biol. Chem., 177, 143-150 (1949). 



66 E. Frolicher and H. Sullmann, Biochem. Z., 274, 21-33 (1934). 



