148 II. DIGESTION AND ABSORPTION OF FATS 



could be shown by a test that an emulsified fat mixture containing some 

 mono- and diglycerides was not absorbed when introduced into the iso- 

 lated loop along with taurocholic acid, but without lipase. 



b'. Phosphorylation and Absorption: According to the Verzar hy- 

 pothesis, phosphorylation is of considerable importance in fat absorption, 

 possibly because of its function in aiding in the resynthesis of fat. Sin- 

 clair 703 believed that the synthesis of neutral fat in the epithelial cells re- 

 sulted by condensation of the fatty acids into a phospholipid, followed by 

 a breakdown of the phospholipid and the formation of neutral fats and the 

 phosphoric acid base complex residue. The latter recombined with new 

 fatty acids to form phospholipids, which continued to assist in the resyn- 

 thesis of the fatty acids into fat. Under such conditions, the phospholipids 

 would play a commanding role in the resynthesis of neutral fats, although 

 the content in the intestinal mucosa would undergo only slight variations 

 during the process. 



On the other hand, Sullmann and Wilbrandt reported a considerable in- 

 crease in phospholipids during the absorption of fat. 616 It was also found 702 

 that, although oleic acid was absorbed from the intestinal loop of a rat in 

 the presence of taurocholate at a fairly rapid rate, the speed of absorption 

 was considerably accelerated when glycerol and phosphate or, especially, 

 glycerophosphate was added to the intestinal loop. This finding has been 

 confirmed by Cera and Bellini. 704 Glycerol or phosphate alone had little 

 effect in altering the rate of absorption of the oleic acid. The beneficial 

 effects of the glycerophosphate on absorption are explained by its stimula- 

 tion of fat resynthesis in the epithelial cells. Since the mucosa of the epi- 

 thelial cells do not have the capacity to store at one time more than a small 

 part of the total fat ingested, when generous amounts of this foodstuff are 

 fed, anything which will cause a rapid transfer of the fat through the cells 

 and into the lymphatic channels will increase the speed of absorption. 

 Since free fatty acids apparently cannot pass into the lymph and remain in 

 the cells until converted to neutral fat, any mechanism which will speed up 

 the resynthesis of neutral fat in these cells will help to prevent a clogging 

 of this portion of the fat-absorption cycle. 



Other experiments of the Verzar group can be interpreted as offering 

 further evidence that the resynthesis mechanism is essential (and indirectly 

 that lipolysis is a necessary prerequisite for absorption). Thus, it was 

 shown that the absorption of olive oil was completely inhibited when sodium 



703 It. G. Sinclair, J. Biol Chem., 82, 117-136 (1929). 



704 B. Cera and L. Bellini, Pathologica, 32, 375-377 (1940); Chem. Abst., 35, 1474 

 (1941). 



