460 IX. CAROTENOIDS AND VITAMINS A 



sin and iodopsin in the retina,--'^ and the astaxanthin-protein complex, 

 known as ovoverdin, in lobsters. -^^--^^ 



In spite of the widespread experimental evidence that /3-carotene and the 

 carotenoids occur in combination with protein, several investigators have 

 indicated the possiblity that they are present in simple aqueous colloidal 

 solutions. Van den Bergh and Muller-^^ observed that carotene could not 

 be readily extracted from simple aqueous colloidal extracts with ether, 

 even though no protein was present. Drummond and McWalter^*^ 

 reported similar results. Although colloidal carotene solutions became 

 unextractable when added to plasma, Dzialoszynski et alr''^ noted that they 

 could be extracted by ether if the plasma protein had been denatm'ed pre- 

 viously. These results do not necessarily preclude the concept that ^- 

 carotene and other carotenoids occur in plasma as protein complexes. In 

 fact, when one considers the positive evidence for such a protein-carotenoid 

 combination together with the indications of a similar phenomenon in the 

 case of vitamin A. which will be given later, this would seem to be the most 

 readily acceptable hypothesis. 



b. Normal Values for Blood Carotene. Blood carotene in normal 

 human subjects has been reported at levels varying between 50 and 500 

 Mg- %, with an average value of 200 Mg- %• Some average figures (in 

 /xg. %) reported include the following: Kimble,-*^ 166 (30 normal men) and 

 187 (34 normal women); Murrill et al.;'^' 213 ± 72; Ralh et al.;-^^ 123; 

 Yarbrough and Dann,^" 183 ± 18.4; Caveness and co-workers, ^^^ 138 

 ± 62; Hsu,293 140 (33 young Chinese adults) and Abels et al.,^^^ 210 (men) 

 and 180 (women). Harris and associates'^^ reported a figure of 210 ±31 

 Mg. % as the average value for seventy normal subjects. Finally, Sin- 



^* R. Kiihn and N. A. Sorensen, Ber., 71, 1879-1888 (1938). 



285 K. Stern and K. Salomon, /. Biol. Chem., 122, 461-475 (1938). 



286 H. H. Van den Bergh and P. Miiller, Proc. Acad. Sci., Amsterdam, 22, 748-757 

 (1920). 



287 J. C. Drummond and R. J. MacWalter, /. Physiol, 83, 23G-242 (1935). 



288 M. S. Kimble, ./. Lah. Clin. Med., 24, 1055-10G5 (1939). 



289 W. A. Mvu-rill, P. B. Horton, E. Leiberman, and L. H. Newburgh, /. Clin. Invest., 

 ;gO, 395-400(1941). 



290 E. P. Ralli, E. Bauman, and L. B. Roberts, /. Clin. Invest., 20, 709-713 (1941). 



291 M. E. Yarbrough and W. J. Dann, /. Nutrition, 22, 597-607 (1941). 



292 H. L. Caveness, G. H. Satterfield, and W. J. Dann, Arch. Ophthalmol, 25, 827-832 

 (1941). 



293 H.-C. Hsu, Chinese Med. J., 61, 238-243 (1943). 



29* J. C. Abels, A. T. Gorham, G. T. Pack, and C. P. Rhoads, J. Clin. Invest., 20, 

 749-764 (1941). 



295 p. L. Harris, K. C. D. Hickman, J. L. Jensen, and T. D. Spies, Am. J. Pub. Health, 

 36, 155-160 (1940). 



