306 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



intestinal tract was immediately removed and kept under anaerobic con- 

 ditions for three hours. More recently, McGillivray 371 demonstrated 

 that highly significant increases in vitamin A occur in sections of sheep 

 intestine incubated with colloidal carotene. Stallcup and Herman 372 

 have likewise proved that the small intestine is one site for the conversion 

 of carotene to vitamin A in the case of dairy calves. However, in this 

 species of animal, the liver was likewise shown to be capable of changing 

 carotene to vitamin A. Rosenberg and Sobel 373 were also able to demon- 

 strate the in vitro conversion of carotene to vitamin A in the isolated small 

 intestine of the rat. In another report, Rosenberg and Sobel 374 showed 

 that the rates of both the in vitro conversion in the small intestine of the 

 rat and the in vivo transformation 375 are markedly diminished in alloxan 

 diabetes. Davies 376 noted that the vitamin A storage in avian coccidiosis 

 is decreased. It is suggested that the invasion of the intestinal wall by 

 coccidia may result in impairment of the conversion of carotene to 

 vitamin A. 



It is reasonable to suppose that the intestinal wall is the site of the 

 transformation of a- and 7-carotenes to vitamin A in species in which 

 carotene is not present in the blood and tissues. That this is the case is 

 indicated by the absence of the carotenoid from the liver of the chicken 

 after the feeding of a-carotene, 377 and its relative absence from the liver 

 of hens after the administration of pro-7-carotene. 378 



One would likewise assume that crypt oxanthin would be acted on by 

 the same enzyme system in the rat as is carotene, to yield vitamin A. 

 That such is the case has been demonstrated by Pat el and co-workers 306 

 for the rat, and by Ganguly and Deuel 307 for the chicken. 



b. Sites for the Conversion of Carotene to Vitamin A Other Than the 

 Small Intestine. Although there is extensive proof that the intestinal 

 mucosa is an important site for the conversion of carotene to vitamin A, 

 some reports would seem to indicate that the same change may be mediated 

 in other tissues. However, the transformation may be carried out less 

 efficiently under the latter conditions. Thus, Bieri and Sandman 249 were 



371 W. A. McGillivrav, Australian J. Sci. Research, B4, 370-376 (1951). 



372 O. T. Stallcup and H. A. Herman, J. Dairy Sci., 33, 237-242 (1950). 



373 A. Rosenberg and A. E. Sobel, Arch. Biochem. Biophys., 44, 320-325 (1953). 



374 A. Rosenberg and A. E. Sobel, Arch. Biochem. Biophys., 44, 326-329 (1953). 



375 A. E. Sobel, A. Rosenberg, and H. Adelson, Arch. Biochem. Biophys., 44, 176-180 

 (1953). 



376 A. W. Davies, Nature, 170, 849 (1952). 



377 J. Ganguly, Personal communication, 1952. 



378 H. J. Deuel, Jr., J. Gangulv, B. K. Koe, and L. Zechmeister, Arch. Biochem.. Bio- 

 phys., 33, 143-149(1951). 



