FACTORS ALTERING CONCENTRATION OF CAROTENOIDS 501 



total vitamin A in the fasting samples, it accounts for only about 10% of 

 the total in the samples at approximately the apex of the plasma vitamin A 

 curve. 



There is a marked sex difference, not only in the basal levels for vitamin A 

 in the plasma, but also during the absorption period, coincident with 

 high vitamin A values. The differences in plasma vitamin A levels be- 

 tween the sexes can be seen from the data summarized in Table 22. 



b'. The Relationship between Plasma and Liver Levels of Vitamin A 

 Alcohol : Lewis and co-workers 884 were of the opinion that plasma tends to 

 resist any changes in vitamin A concentration, despite the wide variations 

 in the amount of vitamin A stored in the liver. This viewpoint has been 

 supported to some extent by the work of several investigators. 836,885-891 

 In fact, in the case of rachitic calves, the plasma vitamin A level is not 

 considered to be a reliable index of the vitamin A intake, 890 of the carotene 

 intake, 892 or of the liver storage of vitamin A. 891 According to Horton et 

 al., ss7 on the other hand, the concentration of vitamin A in the blood is an 

 index of the vitamin A nutrition. Furthermore, Almquist 893 noted that, 

 in chicks and turkeys, plasma vitamin A shows an essentially linear rela- 

 tion to the log of the concentration of vitamin A in the liver. 



Glover and co-workers 132,133 and Horton et a/. 887 suggested that a direct 

 relationship exists between the concentrations of vitamin A alcohol in the 

 liver and in the plasma of rats. Ganguly and Krinsky 894 refuted the con- 

 clusion proposed by Glover et aZ. 132,133 On the basis of experiments in 

 which wide variations were observed in the concentrations of the vitamin A 

 alcohol in the liver, the plasma level for vitamin A alcohol was shown to 

 remain relatively constant. Ganguly et al. 13i postulated that the plasma 

 vitamin A alcohol concentration is determined by the amount of a specific 

 protein carrier in the plasma. 



Aron 895 believes that the liver plays an important role in the regulatory 

 processes controlling the amount of vitamin A circulating in the blood in 



885 H. W. Josephs, Bull. Johns Hopkins Hosp., 71, 253-264 (1942). 



886 S. Brenner, M. C. H., Brookes, and L. J. Roberts, J. Nutrition, 23, 459-471 (1942). 



887 P. B. Horton, W. A. Murrill, and A. C. Curtis, J. Clin. Invest., 20, 387-393 (1941). 



888 A. G. Van Veen, Mededeel. Dienst Volksgesondheid Ned. Indie, 26, 300-307 (1937); 

 cited by P. C. Leong, Biochem. J., 35, 806-812 (1941), p. 806. 



889 R. F. Krause, J. Nutrition, 38, 535-542 (1949). 



890 J. W. Thomas, W. C. Jacobson, and L. A. Moore, J. Dairy Set., 35, 679-686 (1952). 



891 P. C. Leong, Biochem. J., 35, 806-812 (1941). 



892 J. W. Thomas and L. A. Moore, J. Diary Sci., 35, 687-692 (1952). 



893 H. J. Almquist, Arch. Biochem., 39, 243-244 (1952). 



894 J. Ganguly and N. I. Krinsky, Biochem. J., 54, 177-181 (1953). 



895 H. C. S. Aron, Am. J. Diseases Children, 77, 763-773 (1949). 



