ABSORPTION AND TRANSPORT OF FATS 157 



reestablished by the administration of corticosterone, and since it was also 

 improved by the administration of salt solution, 709,710,743 Frazer 645 does 

 not believe that phosphorylation is a prerequisite for fat absorption. 

 Other observations, 738,744 likewise, are considered to support the view that 

 the adrenal cortex is not concerned with phosphorylation in the intestine. 

 Frazer 645 found that the absorption of triglycerides was depressed to 40% 

 following adrenalectomy, while that of fatty acid was practically normal 

 from a quantitative standpoint. If fat is absorbed largely in the form of 

 triglycerides, according to the Partition Hypothesis, then the question of 

 phosphorylation is not relevant. 



The observations of Bavetta and Deuel 686 that a normal absorption of 

 tributyrin occurs following adrenalectomy appear to be in conformity with 

 the idea of particulate absorption. These lower triglycerides are probably 

 completely hydrolyzed to fatty acids and glycerol, and as such would not 

 be subject to particulate absorption. 



Finally, Frazer 645 postulates that at least 60% of the fat absorbed passes 

 through the outer membrane of the epithelial cells in particulate form. 

 This figure is based upon the following considerations: Munk and Rosen- 

 stein 620 were able to account for only 60% of ingested fat in the chyle ob- 

 tained from a thoracic fistula. The fat being absorbed by this route is 

 believed to be derived from material absorbed in particulate form. Sec- 

 ondly, the interference with particulate absorption after adrenalectomy 

 results in a depression to 40% of the normal and, thirdly, lipolysis pro- 

 ceeds to only 30% of completion under the conditions which obtain in the 

 intestine. 



(2) Changes in Fat in the Intestinal Cells 



In considering fat absorption from the small intestine, it is necessary to 

 separate the two phases of the process, namely the transfer of the material 

 from the lumen of the intestine into the intestinal cells, and the discharge 

 of the fat from these epithelial cells into the lacteals and capillaries. Unless 

 both phases of these mechanisms are functioning, absorption of fat may be 

 seriously delayed. 



The actual amount of fat which can be retained at one time in all the 

 intestinal cells is only a fraction of the total absorbed during several hours 

 after a meal containing a generous quantity of fat. The speed with which 

 fat can be absorbed from the lumen of the small intestine will therefore 



743 W. G. Clark and A. N. Wick, Proc. Soc. Expll. Biol. Med., J+-2, 336-338 (1939). 



744 S. Ochoa and R. J. Rossiter, /. Physiol., 97, 1P-2P (1940). 



