CAROTENOIDS AND VITAMINS A IN THE BLOOD 469 



Glover et al.;^^^-^'"^ they were unable to find any relationship between the 

 level of vitamin A alcohol in the hver and that in the plasma in normal male 

 rats, or in those depleted of \dtamin A. In spite of vdde variations in con- 

 centration of vitamin A alcohol in the liver, that in the plasma remained 

 fairly constant. 



b. Normal Values for Vitamin A. The values of plasma vitamin A 

 more or less coincide with those of /J-carotene, the figures normally varying 

 between 20 and 60 /ig- % (67 to 200 I.U.). One International Unit is 

 equivalent to 0.3 /xg. The following averages for plasma \^tamin A (ex- 

 pressed as fjLg. % and as I.U.) have been recorded by various workers: 

 Ivimble,-8» 38 and 27 for men and for women (127 and 91 I.U.); Murrill 

 et air-^' 27.9 (93 ± 15 I.U.); Sobotka,^^« 18 to 24 (60 to 80 I.U.); Ralli and 

 co-workers29o 47.4 (158 I.U.); Yarbrough and Dann,^^! 21.3 (71 ± 33 

 I.U.); Caveness et al.;-^^ 78.9 (263 ± 96 I.U.); Abels and co-workers, ^^^ 

 51 and 44.7 (170 and 149 I.U.); and Harris, Hickman, Jensen and Spies,^^^ 

 61 ± 13 (203 I.U.). Other values reported for special groups of subjects 

 include a figure of 16.8 (56 I.U.) for healthy young Chinese adults, cited 

 by Hsu,-^^ one of 35.4 (118 I.U.) given by Harris and Moore^^^ for normal 

 individuals in Great Britain, and 44.7 (149 I.U.) by Van Bruggen and 

 Straumfjord^^" for hospital patients. Youmans and associates^^^ consider 

 any figure in excess of 21 ng. % (70 I.U.) as normal. However, Sinclair^^^ 

 considers that this figure is the lowest normal value, and that any level 

 below 9 Mg- % (30 I.U.) is abnormally low. Popper and Steigmann^^^ 

 reported average values for 2673 determinations on 454 hospital patients 

 as 58 Mg. % for men and 47 Aig. % for women (193 and 157 I.U., respec- 

 tively). 



So-called "normal" values have also been predicated for a number of 

 animals. Figures as high as 1520 /xg. % were recorded for cows when large 

 amounts of carotene were present in the food, or as low as 140 /zg. % when 

 no green feeds were available. ^^^ In the case of the horse, Rasmussen 

 et al.'-^^ recorded the low average value of 12.5 ± 3.5 jug. % (41.6 I.U.), 

 which is in line with the relatively low figure reported by them for blood 

 carotene. On the other hand, Rudra^^^ cited a mean value of 28 I.U./ 

 100 ml. (8.4/)ug.) for the serum vitamin A of English horses; the val- 



'5s H. H. Sobotka, Personal communication; cited by M. E. Yarbrough and W. J. 

 Dann, J. Nutrition, 22, 597-607 (1947), p. 601. 



3*9 A. D. Harris and T. Moore, Brit. Med. J., 1947, 1, 553-559. 



^ J. T. Van Bruggen and J. V. Straumfjord, /. Lab. Clin. Med., 33, 67-74 (1948). 



361 J. B. Youmans, E. W. Patton, W. R. Sutton, R. Kern, and R. Steinkamp, Am. 

 J. Pub. Health, 34, 368-378 (1944). 



362 M. N. Rudra, Biochem. J., 40, 500-501 (1945). 



