368 V. BLOOD LIPIDS 



sen. 124 Stern and Salomon 125 likewise studied the latter compound, and 

 named it ovoverdin. 



Vitamin A-protein conjugation products also exist in plasma. 6,112,117 

 However, vitamin A ester and vitamin A alcohol are reported to be associ- 

 ated with different proteins in chicken blood. 6 Thus, vitamin A ester was 

 found in the least soluble fraction (globulin), while the free alcohol, to- 

 gether with lutein, was present in the most soluble protein fraction (al- 

 bumin) . In pig plasma, the vitamin A alcohol was also associated with the 

 more soluble protein. Ganguly et al. 6 suggest that species differences in the 

 absorption of carotenoids and of vitamins A may be related to the specific 

 plasma and lymph proteins available for their transport. 



Vitamin A aldehyde (retinene) has likewise been shown to form a com- 

 bination with protein. Thus, Rajagopal and Datta 126 found that, when 

 vitamin A aldehyde and a plasma albumin solution were mixed, a new peak 

 for the absorption spectrum resulted ; this was interpreted as indicating the 

 formation of a new compound. The complex contained 0.968 g. of protein 

 and 2.985 X 10~ 5 g. of vitamin A aldehyde per 100 ml., giving an aldehyde 

 content which was 0.003% of that of protein. 



d. Fat-soluble Vitamins. In addition to the carotenoids, small quanti- 

 ties of several fat-soluble vitamins occur in plasma. Methods are adequate 

 for the accurate determination of vitamins A and E in the blood, but no 

 satisfactory procedure has been evolved for the quantitative assay of vita- 

 mins D and K in the quantity of blood which is ordinarily available. 



(a) Vitamins A . In contrast to the limited occurrence of carotenoids in 

 the blood, vitamin A is distributed almost universally in the blood of all 

 species. This vitamin is present largely as the ester in the blood of rats 

 and pigs. 127,128 Week and Sevigne, 129 using the chromatographic procedure 

 of Glover et al. 130 for the separation of vitamin A alcohol and vitamin A 

 ester, demonstrated that the alcohol is the predominant form of the vitamin 

 in the blood of the fasting individual. However, after vitamin A is ad- 

 ministered, the ester form alone is increased, irrespective of whether the 

 vitamin A was fed as the ester or as the alcohol. 130,131 Whereas only 10 to 

 20% of the total vitamin A was esterified in the blood of their fasting sub- 



124 R. Kuhn and N. A. S0rensen, Ber., 71, 1879-1888 (1938). 



125 K. Stern and K. Salomon, J. Biol. Chem., 122, 461-475 (1938). 



126 K. Rajagopal and P. K. Datta, Nature, 170, 370-371 (1952). 



127 S. Y. Thompson, J. Ganguly, and S. K. Kon, Brit. J. Nutrition, 1, v (1947). 



128 S. Y. Thompson, J. Ganguly, and S. K. Kon, Brit. J. Nutrition, 8, 50-78 (1949). 



129 E. F. Week and F J. Sevigne, J. Nutrition, 40, 563-576 (1950). 



130 J. Glover, T. W. Goodwin, and R. A. Morton, Biochem. J., 4U 94-96 (1947). 



131 H. Hoch, Nature, 158, 59 (1946). 



