192 III. OXIDATION AND METABOLISM 



which organ is responsible for the dehydrogenation. Tangl and Berend^^' 

 suggested that desaturation occurs during absorption from the intestine. 



c'. Saturation of Liver Lipids: Although the liver lipids are usually 

 more highly imsaturated than are other body lipids, this is not invariably 

 the case. Thus, Hilditch^^^ indicated that saturation of unsaturated fats 

 in preparation for storage may be as important a transformation as the 

 reverse change. Rittenberg and Schoenheimer^^^ demonstrated that 

 hydrogenation of unsaturated fats may occur in the animal organism. 

 Mottram^^'' reported that the liver lipids of the plaice had a lower iodine 

 number than did those in the myotomes of the fish. Lovern^^^ also failed 

 to demonstrate desaturation by the liver of the conger eel (Conger vul- 

 garis) or of the porpoise (Phocaena communis). This author^^" reported 

 saturation of the fats of the tmmy {Thunnus thynnus); he noted that the 

 content of stearic acid increased concomitantly with a decrease in the Cis- 

 unsaturated acids. Saturation of fatty acids in the fat depots of the pig 

 was also noted by Banks and Hilditch.'^^ Similar hydrogenation was 

 found in the depot fat of the ox, by Hilditch and Longenecker.^^^ It is 

 suggested that the body attempts to maintain an approximately constant 

 content of saturated acids; this is made possible by the in vivo hydro- 

 genation of the unsaturated Cis acids. 



(b) Fat Transport to and from the Liver. The liver accurately mirrors 

 any change in the mobilization of fats. Thus, Hynd and Rotter^^^ reported 

 that, when mice or rats were given carbohydrate-free diets, the livers of 

 these animals became engorged with fat. When rats were fasted, the 

 livers continued to present increasingly high levels of fat as long as stores of 

 depot fat were available. ^^^~^™ However, in the case of carnivorous 

 animals, such as the dog and cat, whose diet contains little exogenous 

 carbohydrate, liver lipids do not increase to such a marked extent during 

 fasting as they do in other animals. ^^^ 



After fatty meals, the fatty acids in the liver lipids tend to approximate 

 the composition of the ingested fat."^ On the other hand, during fasting, 



«" H. Tangl and N. Berend, Biochem. Z., 220, 234-238 (1930). 



6" V. H. Mottram, J. Physiol., 4-5, 363-369 (1912). 



6«5 J. A. Lovern, Biochem. J., 28, 394-402 (1934). 



«66 A. Hynd and D. L. Rotter, Biochem. J., 24, 1390-1399 (1930). 



667 H. M. Barrett, C. H. Best, and J. H. Ridout, /. Physiol, 93, 367-381 (1938). 



668 J. H. Dible, J. Pathol. Bacteriol, 35, 451-466 (1932). 



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

 R. Whitehead, J. Biol. Chem., 139, 897-915 (1941). 



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

 Taylor, /. Biol. Chem., 143, 473-490 (1942). 



6" R. G. Sinclair, /. Biol. Chem., HI, 515-526 (1935). 



