712 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



resulting from a diet of raw liver, there was a marked increase in the fatty- 

 aldehydes in this organ. 41 



d. Lipoprotein in the Liver. Some of the lipid components in the liver 

 occur in combination with protein. Carver and Thomas 42 made an electro- 

 phoretic study of the lipoprotein of calf liver, and found that it consisted of 

 only one component. A firm combination was shown to exist between the 

 protein and the lipid component. 



e. Free Fatty Acids in the Liver. A number of workers have reported 

 the presence of free fatty acids of high molecular weight in liver. Thus, 

 Bloor and Snider 43 noted that they comprise about one-third of the acetone- 

 soluble extract of liver, while Hilditch and Shorland 33 have also recorded 

 the occurrence of free fatty acids in hepatic tissues. Their presence in 

 liver tissue does not appear to be unique, as they have been found in blood 

 (see page 364), as well as in heart, lung, and kidney, 43 and also in the in- 

 testinal mucosa. 44,45 



Fairbairn 46 cites a value of 2.2 mg./g. of dry fat-free mouse tissue and 

 2.3% of the acetone-soluble fraction of cat liver for the quantity of free 

 fatty acids. There would appear to be some question as to whether or not 

 even these minimum values represent true figures, since a rapid autolysis 

 occurs immediately on removal of the liver, with the formation of free fatty 

 acids. Thus, when rat or cat liver was extirpated, a part of the constituent 

 phospholipids was found to be rapidly hydrolyzed by intracellular phos- 

 pholipases. The extent of hydrolysis amounted to 8% within a few minutes 

 after hepatectomy. When the liver tissue was ground, hydrolysis to the 

 extent of 15% was noted; after the ground tissue was suspended in buffer 

 at pH 7.2 for four hours, as much as 40% of the phospholipid was hydro- 

 lyzed. It is thus questionable whether or not the free fatty acids are nor- 

 mal components of liver tissue; if they are, they represent an extremely 

 minor component, from the quantitative standpoint. 



f. Unsaponifiable Components Present in the Liver, (a) Cholesterol and 

 the Sterols. The sterols constitute the main components of the unsaponi- 

 fiable fraction of liver lipids, from a quantitative standpoint. Freytag 

 and Smith 47 reported that the sterols account for 64% of the total non- 



41 T. Tokushima, M. Yoshihara, and T. Shimojo, J. Biochem. (Japan), 39, No. 5, P5 

 (1952). 



42 M. J. Carver and L. E. Thomas, Arch. Biochem. Biophys., 40, 342-345 (1952). 



43 W. R. Bloor and R. H. Snider, J. Biol. Che?n., 87, 399-413 (1930). 



44 J. A. Lovern and R. A. Morton, Biochem. J., 33, 330-337 (1939). 



46 J. A. Lovern, T. H. Mead, and R. A. Morton, Biochem. J., 33, 338-343 (1939). 



46 D. Fairbairn, /. Biol. Chem., 157, 645-650 (1945). 



47 F. C. Freytag and H.'G. Smith, J. Biol. Chem., 100, 309-317 (1933). 



