FACTORS ALTERING CONCENTRATION OF BLOOD LIPIDS 421 



obviously be the quantity of storage fat available. When these storage 

 depots are exhausted, the protein metabolism is suddenly increased, and 

 death ensues shortly after this so-called "premortal rise." 



The experimental data as to the effect of fasting on the composition of 

 blood lipids have been quite variable. Probably one of the most important 

 factors involved in bringing about this lack of uniformity has been the 

 variation associated with the species of the animal. 



In experiments on dogs, it was reported 221 - 222 ' 393 that either an increase 

 or no change in serum lipids occurred on fasting. Terroine 226 obtained 

 variations in total lipid from +45 to —54% in seven dogs fasted from 

 twenty-two to thirty-five days. Although Greene and Summers 394 dem- 

 onstrated an increase of 200% in the blood fat of fasted puppies, they were 

 unable to find any significant rise in the blood lipids of adult dogs even 

 after prolonged fasting. Underhill and Baumann 395 reported a decrease in 

 blood lipids during the early period of the fast, followed by a rise in blood 

 lipids to normal as the period of the fast progressed. In line with these 

 results, Ling 396 reported a decrease in blood lipids of dogs fasted seven 

 days, while Entenman, Changus, Gibbs, and Chaikoff 397 found no lipemia 

 in dogs subjected to acute fasting for as long as thirty days, or to prolonged 

 undernutrition ; however, when the undernutrition resulted in a severe loss 

 in weight, a decrease in the cholesterol, fatty acids, and phospholipid of the 

 blood ensued. Kartin and associates 398 likewise showed that the blood 

 lipids were not increased in the dog on fasting, although their results on 

 the monkey and on man were somewhat different. 



According to the results of Sure and collaborators, 399 the rat is also a 

 species in which a decrease in the fatty acids and phospholipids of the blood 

 occurs on fasting; blood cholesterol was found to remain constant. How- 

 ever, Kohn 400 reported that the response of blood cholesterol to one week 

 of fasting varied with the strain of the rats. In the case of the Sprague- 

 Dawley and the Osborne-Mendel strains, cholesterol levels reached twice 

 those of the Holtzman and the Tumblebrook hooded strains. This varia- 

 tion in response had a genetic basis which involved a number of genes. 



393 E. Freudenberg, Biochem. Z., 45, 467-487 (1912). 



394 C. W. Greene and W. S. Summers, Am. J. Physiol, 40, 146-147 (1916). 



395 F. P. Underhill and E. J. Baumann, /. Biol. Chem., 27, 169-172 (1916). 



396 S. M. Ling, Chinese J. Physiol, 5, 381-397 (1931 ). 



397 C. Entenman, G. W. Changus, G. E. Gibbs, and I. L. Chaikoff, /. Biol Chem., 

 734,59-69(1940). 



398 B. L. Kartin, E. B. Man, A. W. Winkler, and J. P. Peters, /. Clin. Invest., 23, 

 824-835(1944). 



399 B. Sure, M. C. Kik, and A. E. Church, /. Biol. Chem., 103, 417-424 (1933). 



400 H. I. Kohn, Am. J. Physiol, 163, 410-417 (1950). 



