LIPIDS PRESENT IN LIVER 717 



The lipid content of the liver increases as long as there are available sup- 

 plies of reserve fat, after which a decrease occurs. The increase in liver 

 lipids in response to fasting varies considerably in different species. Thus, 

 the mouse, which is extremely susceptible to fasting, was shown to have the 

 following total lipids during inanition, 86 expressed in mg. per liver: day 

 (unfasted), 66; first day, 107; second day, 110; third day, 42; and fourth 

 day, 20. When expressed on the basis of milligrams per gram moist liver, 

 the figures are 52, 100, 115, 52, and 31 mg. for the prefast day and the four 

 successive fast days, respectively. In later work, Hodge et al. S7 confirmed 

 the fact that liver lipids first increase, then decrease, in the fasted mouse. 

 It was also found 88 that the proportion of phospholipids remains essentially 

 constant in fasting mice. However, since the liver weight decreased by 

 50% during inanition, it is evident that the total phospholipids were also 

 reduced by 50%. In the rat, the variations in liver lipid during fasting 

 are less striking than in the mouse, but the increased values for liver lipids 

 are maintained at the elevated level over a longer period. Thus, Deuel 

 and co-workers 89 found that the values for liver lipid (expressed in % 

 of moist liver weight) were the following in male rats: day (unfasted), 

 3.06; first fast day, 3.90; second fast day, 4.22; third fast day, 4.44; 

 fourth fast day, 3.98; and fifth fast day, 3.89. The values were slightly 

 higher on corresponding days in the case of female rats ; these percentages 

 were 3.34, 4.53, 4.92, 4.55, 5.02, and 5.10, respectively, for the unfasted 

 rats and for those fasted for one to five days. Similar responses to fasting- 

 were reported by other investigators. 90 - 91 Hynd and Rotter 85 noted that 

 cats did not respond to fasting with as pronounced an increase in liver lipids 

 as did mice and rats. During fasting the liver fats rapidly assume the 

 character of the depot fats 86,90,92 whereas, in unfasted animals, the liver 

 lipids tend to display a marked similarity to the food fats. 93 



(a) Fat Turnover in the Liver. The rapidity with which the quantity of 

 fat changes in the liver is a reflection of its rapid turnover in this organ. 



86 P. L. MacLachlan, H. C. Hodge, W. R. Bloor, E. A. Welch, F. L. Truax, and J. D. 

 Taylor, J. Biol. Chem., US, 473-490 (1942). 



87 H. C. Hodge, P. L. MacLachlan, W. R. Bloor, E. Welch, S. L. Romberg, and M. 

 Falkenheim, Proc. Soc. Exptl. Biol. Med., 67, 137-139 (1948). 



88 H. C. Hodge, P. L. MacLachlan, W. R. Bloor, E. Welch, S. L. Romberg, and M. 

 Falkenheim, Proc. Soc. Exptl. Biol. Med., 68, 332-334 (1948). 



89 H. J. Deuel, Jr., M. Gulick, C. F. Grunewald, and C. H. Cutler, J. Biol. Chem., 104, 

 519-530(1934). 



90 H. M. Barrett, C. H. Best, and J. H. Ridout, J. Phxjsiol, 93, 367-381 (1938). 



91 J. H. Dible, J. Pathol. Bacterial., 35, 451-466 (1932). 



92 H. C. Hodge, P. L. MacLachlan. W. R. Bloor, C. A. Stoneburg, M. C. Oleson, and 

 R. Whitehead, /. Biol. Chem., 139, 897-916 (1941). 



93 R. G. Sinclair, J. Biol. Chem., Ill, 515-526 (1935), 



