268 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



uniform for the several species than was observed in these experiments. 

 Cholesterol was apparently absorbed most readily by rabbits, as judged 

 by the effect of cholesterol feeding on plasma cholesterol. These data are 

 summarized in Table 5 (page 267). 



(2) The Digestion and Absorption of Sterols Other Than Cholesterol 



Although cholesterol can readily be absorbed from the small intestine 

 if fat and bile salts are present, many other closely related sterols do not 

 share this property. The first studies in this field were concerned with 

 the plant sterols (phy tosterols) , chiefly sitosterols and stigmasterols. 

 Schonheimer 110-112 found that the phy tosterols are not absorbed even 

 when fed with bile salts. 113 Although Fraser and Gardner 58 originally 

 believed that they had demonstrated the absorption of phytosterols fol- 

 lowed by their conversion to cholesterol, Gardner and Gainsborough 114 

 later agreed with Schonheimer that plant sterols cannot change to chole- 

 sterol in the animal bod}^. The only evidence that phytosterols can be 

 absorbed is that of Nikuni 115 who experimented on mice, and that of von 

 Gierke, who reported tests on rabbits. 116 



In more recent years, considerable additional research has been carried 

 out with individual sterols. Thus Schonheimer 117 and Breusch 118 re- 

 ported that the main group of phytosterols, namely, a mixture of a, /3, 

 and 7-sitosterols, are not absorbed by mice, rats, or rabbits. Rosenheim 

 and Webster 119 noted also that neither stigmasterol nor /3-sitosterol (22- 

 dihydrostigmasterol) is absorbed by rats; the latter was found to be 

 converted to coprostanol. Sperry and Bergmann 120 likewise reported 

 that no increase in liver sterols occurred in mice after sitosterol or stig- 

 masterol was fed. Schonheimer and associates 112 - 113 - 117 reported that, 

 not only was sitosterol not absorbed by rabbits and dogs, but furthermore 



110 R. Schonheimer, Z. physiol. Chem., ISO, 1-5, 16-18. 24-32, 32-37 (1929); 185, 

 119-122(1929). 



111 R. Schonheimer and D. Yuasa, Z. -physiol. Chem., ISO. 6-16, 19-23 (1929). 



112 H. v. Behring and R. Schonheimer, Z. physiol. Chem.. 192, 97-102 (1930). 



113 R. Schonheimer, H. v. Behring, and R. Hummel, Z. physiol. Chem., 192, 117-123 

 (1930). 



114 J. A. Gardner and H. Gainsborough, Quart. J. Med., 23, 465-483 (1930). 



115 J. Nikuni, J. Agr. Chem. Soc, Japan, 7, 827-838 (1931); Chem. Abst., 26, 1323 

 (1932). 



116 E. von Gierke, Verhandl. deut. pathol. Ges., 20th meeting, 1925, p. 159; cited by R. 

 Schonheimer, Z. physiol. Chem., 180, 1-5 (1929), p. 2. 



117 R. Schonheimer, Klin. Wochschr., 11, 1793-1796 (1932). 



118 F. L. Breusch, ./. Biol. Chem., 124, 151-158 (1938). 



119 O. Rosenheim and T. A. Webster, Biochem. J., 85, 928-931 (1941). 



120 W. M. Sperry and W. Bergmann, ./. Biol. Chem., 119, 171-176 (1937). 



