366 V. BLOOD LIPIDS 



fraction containing the /3-carotene is distinct from that with which the 

 vitamin A is combined. 



In addition to /3-carotene, a number of other carotenoids have been dem- 

 onstrated in the blood of several species of animals, but these have been 

 noted only when they were present in the diet. Their occurrence under 

 such conditions can be considered as adventitious. Cryptoxanthin, which 

 is a provitamin A, was reported in the blood serum of cattle, 107 and in that 

 of chickens after it had been administered. 108 In addition, a number of 

 carotenoids which are not precursors of vitamin A have been noted in the 

 blood. These include lycopene (chicken after feeding it, 108 man 109 - 110 ), 

 C4 H 66 , which is an isomer of /3-carotene; lutein (cattle, 107 chicken 108 ), 

 C4oH B4 (OH)2, which is a dihydroxycarotenoid ; and zeaxanthin (chicken 

 after feeding it 108 ), C 4 oHb4(OH) 2 which is an isomer of lutein. Ganguly 

 and co-workers 108 reported that chickens on a farm diet had large quantities 

 of lutein in their blood; however, when they were given a carotenoid-free 

 diet for thirty days, neither lutein nor any other carotenoid was found to 

 be present in the blood. 



(a) The Nature of the Carotenoid and Vitamin A Combinations in the 

 Blood. Recent evidence would seem to indicate that most carotenoids 

 and vitamin A are carried in the blood in the form of loose combinations 

 with protein. As early as 1915, Palmer 111 reported the fact that it was im- 

 possible to extract more than traces of carotene from cow serum by means 

 of ethanol-free ether. This investigator 103 was able to separate a carotene- 

 protein complex from bovine serum which he called "caroto-albumin." 

 On the basis of an ammonium sulfate fractionation, Dzialoszynski and co- 

 workers 112 concluded that, not only carotene, but also vitamin A is associ- 

 ated with a protein factor, which they believed to be an albumin. On 

 the other hand, Bennhold et al., U3 - lu Bendien and Snapper 115 and Mehl 116 



107 A. E. Gillam and M. S. El Ridi, Biochem. J., 29, 2465-2468 (1935). 



108 J. Ganguly, J. W. Mehl, and H. J. Deuel, Jr., J. Nutrition, 50, 59-72 (1953). 



109 E. V. Daniel and G. J. Scheff, Proc. Soc. Exptl. Biol. Med., 33, 26-30 (1935). 



110 E. V. Daniel and T. Beres, Z. physiol. Chem., 238, 160-162 (1936). 



111 L. S. Palmer, J. Biol. Chem., 23, 261-279 (1915); 27, 27-32 (1916). 



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

 (1945). 



113 H. Bennhold, E. Kylin, and S. Rusznyak, Die Eiweisskorper des Blutplasm.as, 

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

 Bluteiweisskorper," pp. 220-303. 



114 H. Bennhold, Verhandl. deut. Ges. inn. Med., 45th Congress, Wiesbaden, April, 

 1933, 357-359. 



115 W. M. Bendien and I. Snapper, Acta Brevia Neerland. Physiol. Pharmacol. Micro- 

 biol, 1, 69-71 (1931). 



116 J. W. Mehl, Personal communication, 1952. 



