420 V. BLOOD LIPIDS 



containing diets were fed to rabbits. Vermeulen and co-workers 389 also 

 reported a considerable rise of the "non-cholesterol fraction" of serum 

 lipids of rabbits fed cholesterol dissolved in sunflower-seed oil. Dubach 

 and Hill 390 observed that the hypercholesterolemia produced in adult white 

 rabbits by feeding either lanolin or cholesterol was invariably accompanied 

 by a lipemia, and by an increase in all blood lipids. A decrease in the 

 albumin : globulin ratio also obtained after two or three months of choles- 

 terol feeding. 



(d) The Effect of Cholesterol Injected Intravenously. Byers and Fried- 

 man 391 prepared a cholesterol suspension which could be injected into 

 rats without producing gross toxicity. Under these conditions, free choles- 

 terol rose to a maximum in the plasma, and decreased gradually for the suc- 

 ceeding forty-eight hours, concomitantly with a rise in the ester fraction. 

 Within thirty-six hours after the injection, however, the cholesterol ester 

 content had returned approximately to the preinjection level. Horlick 

 et aZ. 392 described an intravenous tolerance test for cholesterol in the 

 chicken. 



(3) The Effect of Inanition on the Level of Blood Lipids 



a. The Effect of Complete Starvation. Fat provides the main source 

 for the storage of calories in the animal body. The carbohydrate reserves 

 are relatively small, and are exhausted within two or three days after the 

 initiation of a fast. When this occurs, the body must fall back on its re- 

 serve fat depots as a source of calories. Under this condition, the route 

 of the fat is the opposite of that noted in normal alimentation. Instead of 

 following the usual pathway from the intestinal lumen to the lacteals, to 

 the lymphatics, to the blood stream, to the liver, and then to the fat depots, 

 the course is reversed. The fat in the depots is believed to be taken up by 

 the blood stream, then to be carried to the liver and to the extrahepatic 

 tissues for oxidation. As soon as this mechanism becomes established, the 

 rate of transfer of lipids from the fat stores to the blood stream is adjusted 

 to keep pace with the rate of utilization of this foodstuff by the tissues; 

 a state of equilibrium then is reached. The limiting factor in the continu- 

 ation of this replenishment of the blood lipids from the tissue stores will 



389 C. Vermeulen, L. R. Dragstedt, D. E. Clark, O. C. Julian, and J. G. Allen, Arch. 

 Surg., U, 260-267 (1942). 



390 R. Dubach and R. M. Hill, J. Biol. Chem., 165, 521-531 (1946). 



391 S. O. Byers and M. Friedman, J. Biol. Chem., 177, 841-846 (1949). 



392 L. Horlick, M. Feldman, Jr., and L. N. Katz, Proc. Soc. Exptl. Biol. Med., 168, 243- 

 245 (1948). 



