510 IX. CAROTENOIDS AND VITAMINS A 



vitamin A in the liver and serum of rabbits injected with carotene. The 

 guinea pig is able to accumulate moderate stores of vitamin A when it is 

 given as the preformed vitamin. The stores are rapidly depleted when the 

 intake of vitamin A is reduced. ^^^ 



Rodahl and Moore^^* recorded extremely high values for vitamin A in the 

 case of polar bears, and sometimes in seals. It is believed that the seal ob- 

 tains its vitamin A from the cod and other fishes upon which it preys, while 

 the polar bear is believed to derive its high store of vitamin A from the seal, 

 which constitutes its main article of diet. Presumably because of the high 

 concentration of vitamin A in the livers of polar bears, these organs are 

 toxic; this toxicity has been repeatedly demonstrated among Arctic ex- 

 plorers since Elizabethan times. ^^^ The high vitamin A content of whale 

 liver was accounted for by Kon and Thompson^** on the basis of the pre- 

 formed vitamin A present in the ocean plankton shrimps upon which the 

 animals subsist. It is recognized by Moore-^^ that the values recorded 

 for the several species "can be considered to be typical only when they are 

 related to a characteristic nutritional background." 



The tissues of several other species of animals contain a minimum amount 

 of carotene. Thus, the flesh of the carabao or Philippine water buffalo 

 (Buhalus kerabau) has 0.2 Mg-Zg- of carotene, in spite of the fact that the 

 body fat is colorless. ^^^ ;S-Carotene is the only carotenoid present in the 

 corpus luteum of the Nubian wild ass (Equus asinus (africanus)) .^^~ 

 Only traces of carotene have been reported in the liver of the dog.^^* 



a'. Man: Man absorbs and stores the carotenoids unselectively. The 

 blood carotenoids, those stored in the liver and depots, as well as those 

 secreted into the milk, usually reflect the type of pigments which are pre- 

 sent in the diet. In addition to /3-carotene,''" human fat may contain a- 

 carotene,^^^"^^^ lutein,-*'^^ zeaxanthin,-^ capsanthin,-^'^^ and lycopene.-'''^'" 

 The only carotenoids which have been considered to be non-absorbable are 

 the epoxides.^^^ 



Carotenoids likewise occur in many tissues other than fat depots, and 

 the proportion of the several carotenoids corresponds to that in the diet. 

 This relationship has been established in human subjects and in other 



553 L. S. Bentley and A. F. Morgan, J. Nutrition, 30, 159-169 (1945). 

 59" K. Rodahl and T. Moore, Biochem. J., 37, 106-168 (1943). 



595 E. V. Rouir, Bull. soc. chim. biol, 29, 754-755 (1947). 



596 L. Zechmeister, Bull. soc. chim. biol, 16, 993-1008 (1934). 

 5" J. G. Thomson, Z. ges. exptl. Med., 92, 692-710 (1934). 



598 P. Karrer and E. Krause-Voith, Helv. Chim. Acta, 31, 802-803 (1948). 



