FACTORS AFFECTING RATE OF ABSORPTION 193 



given by stomach tube or was injected into the intestine. 701 Moreover, not 

 only was the absorption of fat prevented, but a similar inhibition in the 

 absorption of fatty acids was noted. In this case one cannot level the same 

 criticism as regards toxicity as applies to monoiodoacetate, since phlo- 

 rhizin is much less toxic. 867 



As in the case of monoiodoacetate, the inhibitory activity of phlorhizin 

 has been ascribed to its interference with phosphorylation, which Verzar 564 

 considers an essential step in the absorption of fatty acids. However, the 

 interference, with fat absorption in the case of both monoiodoacetate and 

 phlorhizin is not concerned with inability to transfer the fatty acid to the 

 intestinal mucosa, but rather with the absence of synthesis of neutral fat 

 within the cell. Verzar 564 assumes that the change of the fatty acid into 

 the triglyceride involves an intermediate phosphorylation, and that this 

 reaction cannot occur when inhibitors are present. Frazer, 646 on the other 

 hand, discounts the validity of the experiments with phlorhizin and with 

 monoiodoacetate, on the basis that the doses used were excessively large 

 and caused extensive damage to the intestinal mucosa. 761 



(6) Miscellaneous Factors Affecting Fat Absorption 



Frazer 868 reported that the rate at which fat was absorbed was acceler- 

 ated if choline was given. After olive oil and water were administered, 

 the intestinal cells were filled with large globules of fat, while very little 

 appeared to have passed through into the areolar tissue of the villi or into 

 the lacteals. When choline was added, masses of fat could be seen in the 

 areolar tissue of the villi, and the cells were more rapidly cleared. The 

 fat remaining in the cells appeared to be more finely dispersed. It is 

 possible that this increase in rate of absorption is related to the similar 

 effect noted when lecithin was included in the diet. 816 



Stamp 869 reported that the absorption rate was augmented in rabbits 

 subjected to prolonged exposure to reduced atmospheric pressure, as indi- 

 cated by a marked lipemia; however, MacLachlan and Thacker 870 were 

 unable to demonstrate any interference with the absorption of fat within 

 ranges of anoxia compatible with life. Although x-radiation was shown to 

 bring about an increased tone and motility in the gastrointestinal tract of 

 rats, Mead et a 7 .. 871 found that the absorption rate of fats was essentially 



867 L. V. Beck, J. Biol. Chem., 143, 403-415 (1942). 



868 A. C. Frazer, Nature, 157, 414 (1946). 



869 U. Stamp, Biochem. Z., 270, 74-92 (1934). 



870 P. L. MacLachlan and C. W. Thacker, Am. J. Physiol., 143, 391-395 (1945). 



871 J. F. Mead, A. B. Decker, and L. R. Bennett, ./. Nutrition, 43, 485-499 (1951). 



