THE DIGESTION OF FATS 139 



It is well known that the duration of the absorption period of moderate 

 doses of fat is only five hours. Frazer 645 states the crux of his argument as 

 follows : 



"If the end-products of hydrolysis during the first five hours are fatty 

 acids and glycerides, and over 90% of the fat is absorbed during this period, 

 it is obvious that a significant proportion of the fat must be absorbed as 

 unhydrolysed or partly hydrolysed triglyceride." 



A number of investigators have confirmed the demonstration by Frazer 

 and Sammons 647 that only a partial hydrolysis of fat occurs in the small 

 intestine. Desnuelle et al. 6i8 reported that the hydrolysis of coconut oil, 

 peanut and sunflower oils, when catalyzed in vitro by pancreatic lipase, 

 gives rise to only a minimum quantity of free fatty acids. The action of 

 pancreatic lipase on triglycerides was shown to be a three-stage reac- 

 tion. 649 ' 650 First, a rapid formation of diglycerides obtains, while the second 

 and third stages, which involve the removal of the second and third fatty 

 acid from glycerol, proceed very slowly. It is suggested that the affinity 

 of lipase for the glycerides diminishes with the appearance of free hydroxyl 

 groups. The digestion mixture present, when triglycerides and pancreatin 

 are incubated over a period of one to four hours, in the absence of calcium, 

 consists largely of unattacked triglycerides, of diglycerides, of small 

 amounts of monoglycerides, and of traces of glycerol. 651 Artom and Reale 

 were the first to make the observation that mono- and diglycerides are 

 formed in both the digestion 652 and the synthesis 34 of fats by pancreatic 

 lipase. Kuhrt and associates 653 reported that 37 to 50% of the lipids in the 

 intestinal lumen of human subjects after fatty meals consisted of mono- 

 glycerides. 



On the other hand, Desnuelle et a/. 654 - 655 reported that the presence of 

 calcium ions in the gastrointestinal tract of rats and dogs augments the 

 proportion of monoglycerides at the expense of the diglycerides. The 

 same ratio of acids and partial glycerides was shown to be present when the 



648 P. Desnuelle, M. Naudet, and J. Rouzier, Arch. sci. physiol., 2, 71-79 (1948). 



649 P. Desnuelle, M. Naudet, and J. Rouzier, Compt. rend. soc. biol., 11,1, 1242-1244 

 (1947). 



650 P. Desnuelle, M. Naudet, and M. J. Constantin, Compt. rend. soc. biol, 144, 1182- 

 1183 (1950). 



651 P. Desnuelle, M. Naudet, and J. Rouzier, Biochim. et Biophys. Acta, 2, 561-574 

 (1948). 



652 C. Artom and L. R6ale, Arch. sci. biol. (Italy), 21, 368-380 (1935). 



863 N. H. Kuhrt, E. A. Welch, W. P. Blum, E. S. Perry, W. H. Weber, and E. S. 

 Nasset, J. Am. Oil Chemists' Soc, 29, 271-278 (1952). 



664 P. Desnuelle and M. J. Constantin, Biochim. et Biophys. Acta, 9, 531-537 (1952). 



655 P. Desnuelle, M. Naudet, and M. J. Constantin, Biochim. et Biophys. Acta, 5, 561- 

 568(1950). 



