6 II. DIGESTION AND ABSORPTION OF FATS 



The regurgitation of intestinal contents may aid in lipolysis, both by 

 furnishing additional lipase, and by producing a reaction of the gastric 

 contents near to the optimum pH of gastric lipase. While the gastric 

 digestion of fats is of only minor importance in itself, it does provide some 

 free fatty acids which accelerate the rate of emulsification of the lipids, 

 once the chyme is passed into the small intestine. 



A suggestion as to another possible source of gastric lipase in certain 

 species has been offered by Famham. 8a He stated that a lipase is secreted 

 in the calf, kid, and lamb by a gland located at the base of the tongue and 

 extending downward into the gullet area. This enzymatic secretion 

 would naturally pass into the stomach. The gland is now being employed 

 commercially as a source of enzymes which are utilized in the cheese in- 

 dustry for the development of flavor. 8b 



b. Pancreatic Lipase (Steapsin). The action of pancreatic juice in 

 causing emulsification and hydrolysis of fats was first recognized in 1856 

 by Claude Bernard. 9 This enzyme was further studied by Herter (1880), 10 

 by Glaessner (1904), n by Bradley (1909), 12 and by Wohlgemuth (1912), 13 

 while Pavlov 14 reported at length on the lipase present in the pancreatic 

 juice of the dog. The collection of pancreatic juice was greatly aided by 

 the discovery that the principal stimulus to secretion is controlled by a 

 humoral mechanism. 15 Ivy 16 reviewed the mechanism of secretion of 

 pancreatic juice, as well as that of other digestive secretions. 



Steapsin is the most important enzyme involved in the digestion of neu- 

 tral fat. It is secreted by the acinar cells of the pancreas, along with the 

 accompanying enzymes, trypsin, chymotrypsin, and amylopsin. 



(a) Activation of Pancreatic Lipase by Bile Salts. Steapsin, as secreted, 

 is partially inactive. It was formerly believed that this lipase was produced 

 as an inert zymogen called "steapsinogen," which was converted to the 

 active form in the small intestine by contact with bile salts. However, 

 bile salts have been shown to activate both gastric and pancreatic lipase 



8a M. G. Farnham, personal communication to the author (March, 1954). 

 8 b M. G. Farnham, U. S. Patent No. 2,531,329 (Nov. 21, 1950). 



9 C. Bernard, Mbnoire sur le pancreas et sur la role du sue pancreatique dans les 

 phinomenes digestifs, partiadierement dans la digestion des matieres grasses neutres, 

 Balliere, Paris, 1856. 



10 E. Herter, Z. physiol. Chem., 4, 160-164 (1880). 



11 K. Glaessner, Z. physiol. Chem., 40, 465-479 (1904). 



12 H. C. Bradley, J. Biol. Chem., 6, 133-172 (1909). 



13 J. Wohlgemuth, Biochem. Z., 39, 302-323 (1912). 



14 1. P. Pavlov, The Work of the Digestive Glands, translated by W. H. Thompson, 2nd 

 English ed., Griffin, London, 1910. 



16 W. M. Bayliss and E. H. Starling, J. Physiol., 80, 61-83 (1904). 

 16 A. C. Ivy, Physiol. Revs., 10, 282-335 (1930). 



