ABSORPTION AND TRANSPORT OF PATS 147 



of the twentieth century; it has been thrown open to question only com- 

 paratively recently by Frazer, 700 who pointed out certain phenomena which 

 cannot be explained by such an hypothesis. 



a'. The Hydrotropic Action of Bile Salts: According to the Verzar 

 theory, the fatty acids are brought into diffusible form by the hydrotropic 

 action of the bile salts. It was postulated that the fatty acids form com- 

 binations with the bile salts similar to the choleic acids demonstrated by 

 Wieland and Sorge 506 ; these complexes are conveyed through the intestinal 

 wall, whereupon the bile salt plus fatty acid combination is broken up within 

 the cell, and the bile salts are set free, to be excreted and to aid in the ab- 

 sorption of more fatty acids. It is suggested that the bile salts may be 

 adsorbed to the surface of the epithelial cells, where they are able to dis- 

 solve more fatty acid molecules and to transport them into the cells. 



Although the importance of choleic acid may be somewhat overempha- 

 sized, since such complexes have been isolated only for desoxycholic and 

 apocholic acids in a non-conjugated form, convincing experiments indicate 

 the importance of the conjugated bile salts in solubilizing the fatty acids. 

 Verzar and Kuthy 513 were able to obtain clear soap solutions with oleate, 

 palmitate, and stearate at pH values of 8 to 9; however, clear solutions of 

 these soaps could be formed with conjugated bile salts at pH values of 6.18, 

 6.35, and 6.16, respectively. Thus, it was possible to obtain the fatty 

 acids in soluble and diffusible form in vitro, on the acid side of neutrality, in 

 a pH range at which the unconjugated bile acids do not dissolve. 



The role of the bile acids in aiding in fat absorption has likewise been 

 proved by the in vivo experiments of Verzar and Laszt. 701,702 When olive 

 oil alone was added to isolated intestinal loops of dogs, no absorption 

 occurred. The same results were found when taurocholic acid was added 

 to the olive oil. Negative results were likewise noted when the fat and an 

 active lipase preparation were placed in the intestinal loop. Positive re- 

 sults were obtained only when a mixture of fat, lipase, and taurocholic 

 acid was employed. Thus, hydrolysis alone is not enough to effect ab- 

 sorption. Moreover, bile salts are unable to dissolve unhydrolyzed fat. 

 This would seem to offer cogent proof for the lipolysis theory. However, 

 the results do not completely negate the hypothesis of Frazer 645 that a mini- 

 mum amount of hydrolysis occurs, with the resultant formation of di- and 

 monoglycerides, which are required to render possible the formation of a 

 satisfactory emulsion. This criticism could be adequately disproved if it 



700 A. C. Frazer, Arch. sci. physiol., 2, 15-41 (1948). 



701 F. Verzar and L. Laszt, Biochem. Z., 270, 35-43 (1934). 



702 F. Verzar and L. Laszt, Biochem. Z., 270, 24-34 (1934). 



