CAROTENOIDS AND VITAMINS A IN THE BLOOD 459 



this group is less certain. Ganguly and co-workers-" reported that the 

 plasma \'alue of rats contains no carotenes or xanthophylls. Goodwin^^- 

 i-eported that xanthophylls are ne\'er found in the portal or systemic blood 

 of rabbits. 



a. The Nature of the Carotenoids in the Blood. Considerable evidence 

 has accvunulated in support of the concept that, when /5-carotene and other 

 carotenoids occur in the blood, they do so in combination with protein. In 

 1915-1916, Palmer-^^'-^'' called attention to the fact that the carotene was 

 not directly extractable from cow serum by means of ethanol-free ether. 

 Later Palmer and Eckles-^^ prepared the so-called "caroto-albumin" from 

 cow serum which was believed to be the combination normally occurring 

 in blood. Dzialoszynski et al^''^ were of the opinion that carotene was 

 combined with an albumin fraction in human blood, but later workers^^®"^^" 

 believed that the carotene-containing protein was a /3-globulin. In the re- 

 cent report of Oncley et al.-^^ and that of Cohn and co-workers,-*- it was 

 noted that carotenoids were present in human blood in the /^-lipoprotein 

 fraction. Ganguly et alr^"^ reported that vitamin A ester occurred in the 

 least soluble fraction in chicken plasma, and vitamin A alcohol and lutein 

 in the more soluble fractions. In beef blood, /S-carotene occurred along 

 with lutein and vitamin A alcohol in the more soluble (presumably albumin) 

 fraction. In pig plasma, vitamin A alcohol was associated with the less 

 soluble protein. 



Additional evidence, which supports the concept that ;S-carotene and 

 carotenoids in blood are combined with protein, is to be gleaned from the 

 number of protein complexes of carotenoids which occur in nature. These 

 include the lycopene-protein complex in tomato,-*^ rhodopsin, porphj^rop- 



275 L. M. Dzialoszynski, E. M. Mystkowski, and C. P. Stewart, Biochem. J., 39, 63-69 

 (1945). 



^''^ H. Bennliold, E. Kylin, and S. Ruszynj^dk, Die Eiiveisskorper des Bhdplasmas, 

 Steinkopff, Dresden-Leipzig, 1938; Chap. 7, H. Bennhold, Die Vehikelfunktion der 

 Bluieiiveisskorper, pp. 220-303. 



"' H. Bennhold, Verhandl. deut. Ges. inn. Msd., 45th Congress, Wiesbaden, April, 

 1933, 357-359. 



278 \y ]yj Bendien and I. Snapper, Acta Brevia Neeiiand. Physiol., Pharumcol. Micro- 

 biol., 1, 69-71 (1931). 



2" J. W. Mehl, Personal communication, 1952. 



280 L. B. Pett and G. A. LePage, /. Biol. Chetn., 132, 585-593 (1940). 



281 J. L. Oncley, F. R. N. Gurd, and M. Melin, /. Am. Chetn. Soc, 72, 458-464 (1950). 

 2S2 E. J. Cohn, F. R. N. Gurd, D. M. Surgenor, B. A. Barnes, R. K. Brown, D. 



Derouaux, J. M. Gillespie, F. W. Kahnt, W. F. Lever, C. H. Liu, D. Mittelman, R. F. 

 Mouton, K. Schmid, and E. Uroma, /. Am. Chen. Soc, 72, 465-474 (1950). 

 283 R. Kuhn and H. J. Bielig, Ber., 73, 1080-1091 (1940). 



