STORAGE OF CAROTENOIDS AND OF VITAMINS A 521 



present in the liver of the normal weanling rat increases rapidly during the 

 period of rapid growth, and reaches a maximum concentration at 170 days. 

 After this period, additional vitamin A is stored, but the concentration in 

 the liver remains constant. The data for these experiments are sum- 

 marized in Table 1 . 



Table 1 



Vitamin A Content of the Livers of 

 Stock Rats op Various Ages" 



" Adapted from N. B. Guerrant, J. Nutrition, 37, 37-51 (1949), p. 41. 



The low vitamin A level reported in the livers of newborn rats (7 I.U./rat 

 or 20 I.U./g. of liver) is in agreement with the results obtained by William- 

 son, ^^^ who computed the total vitamm A in the livers of unborn rats. 

 This figure apparently is an index of the amount of vitamin A imparted to 

 the fetal rats through the placental circulation. Eaton and co-workers^^^ 

 and Baker et al.^'"^ observed that the vitamin A stored by the calf during in- 

 trauterine life varies with the vitamin intake of the mother, since the 

 plasma level of vitamin A of the newborn calf is higher, and there is a 

 greater storage of vitamin A in the liver at ten days after birth in calves 



«" H. D. Eaton, A. A. Spielman, R. E. Johnson, and L. D. Matterson, /. Dairy Sci., 

 3^,764-768(1949). 



"4 F. H. Baker, R. MacVicar, L. S. Pope, and C. K. Whitehair, Proc. Soc. Exptl. Biol. 

 Med., 83, 571-574 (1953). 



