CHOLESTEROL IN THE BLOOD 375 



pjgg 123.124 g^j^fj dogs.^-^ In the case of rabbits fed cholesterol along with 

 bile salts, atherosclerosis'-®-^" may be observed to accompany the hyper- 

 cholesterolemia. '-^ 



Fasting may cause an alteration in the level of blood cholesterol; how- 

 ever, the rat'-^ and the dog ordinarily do not show any change in blood 

 cholesterol'^" or in the degree of lipemia in general,'^' during inanition, un- 

 less there is a severe loss of weight due to the undernutrition.'^" Mice,'^- 

 rabbits,'^^'^* and man'^^ usually develop higher than normal blood choles- 

 terol levels during fasting. However, Shope'^* observed a hypocholes- 

 terolemia in the cat, guinea pig, swine, and, in some cases, in man under 

 conditions of dietary restriction. 



Not only fasting, but also the absence of essential fatty acids in the diet 

 results in hypocholesterolemia in rats,'*^ associated with an increase in the 

 cholesterol content of the liver and adrenal glands. On the other hand, 

 when the diet contained 12.5 per cent of cottonseed oil, the blood choles- 

 terol remained constant and no excess cholesterol was found to be de- 

 posited in the liver or adrenals. It is believed that essential fatt}^ acids 

 must be present in the diet to insure a normal cholesterol metabolism. 



(3) Pathologic Factors Altering Blood Cholesterol 



The thyroid is the most important of the endocrine glands as regards the 

 control of cholesterol metabolism. Hypercholesterolemia is an invariable 

 consequence of thyroid undersecretion, while hypocholesterolemia results 

 from hypersecretion of this gland. 



Following extirpation of the thyroid gland, high serum cholesterol levels 



12* R. Okey, Proc. Soc. Exptl. Biol. Med., 51, 349-350 (1942). 



125 A. Knudson, J. Biol. Chem., 45, 255-262 (1921). 



126 K. B. Turner, /. Exptl. Med., 58, 115-125 (1933). 



127 K. B. Turner and E. H. Bidwell, /. Exptl. Med., 62, 721-732 (1935). 



128 L. Swell and D. F. Flick, .4m. J. Physiol., 174, 51-53 (1953). 



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



1™ C. Entenman, G. W. Changus, G. E. Gibbs, and I. L. Chaikoff, J. Biol. Chem., 134, 

 59-69 (1940). 



1" B. L. Kartin, E. B. Man, A. W. Winkler, and J. P. Peters, J. Clin. Invest., 23, 824- 

 835(1944). 



132 P. L. MacLachlan, /. Biol. Chem., 152, 391-394 (1944). 



1" R. E. Shope, J. Biol. Chem., 75, 101-113 (1927). 



13* G. W. Ellis and J. A. Gardner, Proc. Roy. Soc. (London), B 85, 385-393 (1912). 



135 C. Fahrig and L. Wacker, Klin. Wochschr., 11, 886-891 (1932). 



136 R. B. Alfin-Slater, L. Mtergood, A. F. Wells, and H. J. Deuel, Jr., Arch. Biochem. 

 Biophys., 52, 180-185 (1954). 



