140 II. DIGESTION AND ABSORPTION OF FATS 



fat was treated with lipase in vitro and in vivo, in the case of the intraluminal- 

 lipids. In a later report, Desnuelle and co-workers 656 stated that about one- 

 third of the fat is completely hydrolyzed by pancreatic lipase while the 

 remaining two-thirds is in the form of mono- and diglycerides. 



Several workers have investigated the extent of hydrolysis of fats, using 

 tagged glycerol. Thus, Favarger et al. 6b7 found that trielaidin containing 

 deuterioglycerol was hydrolyzed to the extent of only 5% in rats, as deter- 

 mined from the proportion of glycerol incorporated into intestinal fats and 

 blood. Reiser and associates 658 noted that 25 to 45% of the ingested glycer- 

 ides are completely hydrolyzed during absorption, while the remaining 

 glycerides are converted to monoglycerides. The hydrolyzed glycerol was 

 not used for the resynthesis of fat, but it followed an independent meta- 

 bolic pathway. It was shown that about 50% of the phospholipid present 

 in lymph formed from ingested fat utilized the hydrolyzed fatty acids and 

 endogenous glycerol. Morehouse and Skipski, 659 using dioleyl-deuterio- 

 stearin containing C 14 -labeled glycerol, demonstrated that some break- 

 down of lipid material took place in the gastrointestinal tract, with a sub- 

 sequent recombination. The possibility that unchanged neutral fat may 

 be absorbed was indicated. 



A quantitative evaluation of the nature of the intestinal contents after a 

 fat meal has been made possible by the separation of the mixture into its 

 several components by the use of a countercurrent analytical procedure, 

 by Mattson and his associates. 640 The results of these investigators support 

 the Frazer hypothesis. The mono- and diglycerides isolated from the in- 

 testinal contents of rats four hours after fat feeding accounted for 16 and 

 36% of the total lipids. Moreover, the hydrolysis of the fatty acids from 

 the glycerol moiety was found to proceed by a definite pathway rather than 

 in a random fashion. Thus, evidence was adduced that the diglycerides 

 formed were of the l,2-(a,/?) variety. The monoglycerides initially formed 

 consisted practically entirely of the 2-isomer, although this compound was 

 found to be labile and readily changed to the l-(a) isomer by the manipula- 

 tive procedures. Confirmatory evidence for this sequence in hydrolysis 

 has been obtained in in vitro studies with tripropionin. Sch0nheyder and 

 Volqvartz 660 demonstrated that, when liver esterase or pancreatic lipase 



656 P. Desnuelle, M. Naudet, and M. J. Constantin, Biochim. et Biophys. Acta, 7, 251- 

 256 (1951). 



667 P. Favarger, R. A. Collet, and E. Cherbuliez, Helv. Chim. Acta, 84, 1641-1654 

 (1951). 



858 R. Reiser, M. S. Bryson, M. J. Carr, and K. A. Kuiken, J. Biol. Chem., 19/,, 131- 

 138 (1952). 



669 M. G. Morehouse and W. Skipski, Federation Proc, 12, 248-249 (1953). 



660 F. Sch0nheyder and K. Volqvartz, Biochim. et Biophys. Acta, 8, 407-415 (1952). 



