680 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



creased amounts of both glycerides and cholesteryl esters, 845 but essentially 

 normal amounts of phospholipids. 



Although all types of fatty livers contain a certain proportion of chole- 

 sterol, the quantity of this sterol stored in the liver, chiefly in the form of 

 the ester, is greatly increased after cholesterol is introduced into the 

 diet. 556 ' 845-847 Concomitantly, the cholesterol ester fraction is reduced in 

 the serum. 554 ' 789 ' 847 Li and Freeman 848 have shown that cholesterol feeding 

 also results in a higher cholesterol and lipid content in the liver of the pro- 

 tein-deficient dog. In opposition to the results on rats, these workers re- 

 port an increase in the amount of free cholesterol, as well as of cholesterol 

 ester, in the livers of these animals. According to Clement and asso- 

 ciates, 849 the fatty infiltration occurring when 3 to 5% of cholesterol is 

 included in the diet consists entirely of free lipids, not linked to cellular 

 structures. 



Fatty livers resulting from cholesterol are more resistant to choline 579 

 than are other types of fatty livers, although the fatty infiltration can be 

 prevented if sufficiently large doses of choline are given. 823 Whereas 2 g. of 

 casein per lb. of body weight sufficed to prevent fatty livers in dogs on a 

 high-fat diet, this amount was found to be insufficient to prevent the cho- 

 lesterol type of fatty liver. 848 The cholesterol esters appeared to be espe- 

 cially resistant to all lipotropic agents. On the one hand, Ridout and col- 

 laborators 845 were able to control the triglyceride content of the livers of rats 

 on lipotropic cholesterol diets; on the other hand, the cholesterol esters in 

 this organ were slightly increased when the choline intake was highest, even 

 when the cholesterol level in the diet was lowest. However, Benard et 

 al. Si7 reported that, when rats having fatty livers of dietary origin or due to 

 poisoning were injected with choline or methionine, the ratio of ester to 

 total cholesterol was reduced from 0.419 to 0.185 and 0.192, respectively, as 

 compared with a normal ratio of 0.165. 



The mechanism of action of cholesterol in producing fatty infiltration of 

 the liver has not been explained. It has been suggested that cholesterol 

 acts as a vehicle for transporting fatty acids from the intestinal wall to the 

 liver, but this leaves open to question the mode of transfer of the fatty acid 

 to another alcohol in the liver. Only a limited amount of cholesterol is 



845 J. H. Ridout, C. C. Lucas, J. M. Patterson, and C. H. Best, Biochem. J., 52, 79-83 

 (1952). 



846 R. P. Cook, Biochem. J., SO, 1630-1636 (1936). 



847 H. Benard, A. Gajdos, and M. G. Torok, Compt. rend. soc. biol, 144, 762-764 

 (1950). 



848 T. W. Li and S. Freeman, Am. J. Physiol, 145, 645-659 (1946). 



849 G. Clement, J. Clement, and E. Le Breton, Compt. rend., 284, 2006-2008 (1952). 



