286 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



b'. The Effect of Bile on the Absorption of /3-Carotene: One of the 

 important conditions controlling absorption is the presence of bile. 

 In any condition in which there is an hepatic dysfunction, such as an ob- 

 structive jaundice, or in any other situation in which biliary flow is im- 

 paired, the absorption of carotene and, in fact, of all other fat-soluble 

 vitamins (except vitamin A), is greatly decreased. The bile salts have 

 been shown to be the active agents, present in bile, effecting the absorption 

 of carotene. 



Greaves and Schmidt 221 proved that bile acids such as glycodesoxycholic 

 and desoxycholic acids are required for the absorption of carotene in 

 vitamin A-deficient, choledochocolostomized rats, as judged by a bio- 

 assay for vitamin A based upon the vaginal smear technic. Orally ad- 

 ministered carotene proved to be ineffective in overcoming the vitamin 

 A deficiency in such animals, although vitamin A itself gave positive 

 results. When bile salts were administered in the diet of the operated 

 rats, carotene was absorbed. In later work, 222 it was shown, in confirma- 

 tion of these earlier results, that carotene could not be utilized in jaundiced 

 rats or in those in which the liver injury was produced by phosphorus 

 poisoning, although vitamin A was still effective. Similar convincing 

 experiments, on isolated intestinal loops of dogs, have also been reported 

 by Irvin et al. 223 Insignificant amounts of the provitamin were absorbed 

 when carotene was introduced into the intestinal loops in cottonseed oil 

 solution. However, when either gall-bladder bile (from ox or hog) or 

 pancreatic lipase was given concomitantly, considerable amounts of caro- 

 tene were utilized. Best results were obtained when bile salts and pan- 

 creatic lipase were both added to the intestinal loop along with the cot- 

 tonseed oil solution of carotene. One may assume that the bile salts pro- 

 duce their effect on carotene absorption by the formation of a choleic 

 acid-like compound with carotene. 



c'. The Effect of Simultaneous Fat Feeding on the Absorption of (3- 

 Carotene: Another factor of considerable importance in effecting caro- 

 tene absorption is the nature of the solvent in which the carotenoid is 

 dissolved. 224 - 225 Thus, when the provitamin A is dissolved in fat, utiliza- 

 tion may occur whereas, in the absence of fat, the carotenoid may not be 

 absorbed from the intestine. Both rats and cats were shown by Ahmad 226 



221 J. D. Greaves and C. L. A. Schmidt, Am. J. Physiol, 111, 492-501 (1935). 



222 J. D. Greaves and C. L. A. Schmidt, Am. J. Physiol, 111, 502-506 (1935). 



223 J. L. Irvin, J. Kopala, and C. G. Johnston, Am. J. Physiol, 132, 202-209 (1941). 



224 E. J. Lease, J. G. Lease, H. Steenbock, and C. A. Baumann, ./. Nutrition, 17, 91- 

 102 (1939). 



225 H. C. Sherman, /. Nutrition, 22, 153-165 (1941). 



226 B. Ahmad, Biochem. J., 25, 1195-1204 (1937). 



