METABOLISM OF CAROTENOIDS AND VITAMINS A 553 



Rehydrovitamiii A, rather than vitamin A itself, is deposited in the Hvers 

 of rats after anhydrovitamin A is fed.*^'*" It was given this name for the 

 reason that, although the new molecule is formed by the addition of a 

 molecule of water, the double bond system differs from that of vitamin A. 

 The biopotency of rehydrovitamin A was found by Shantz^^^ to be about 

 one-fifteenth of that of vitamin A. For the structures and properties of 

 anhydrovitamin A and rehydrovitamin A the reader is referred to The Lip- 

 ids, Vol. I, pages 733-738. 



d. The Vitamin A-Like Effect of Lard. Although lard is generally 

 believed to be tlevoid of vitamin A, Kaunitz and Slanetz^'*-'^''^ demonstrated 

 the presence of a factor in a molecular distillate of lard which protected 

 rats against the signs of vitamin A deficiency. It was first considered that 

 this factor was distinct from vitamin A; in fact, a number of workers^** ~^^^ 

 suggested the presence of substances in foods which possessed biologic ac- 

 tivity but which were assumed to be chemically different from the known 

 vitamins A. These substances included lard, oils from the decapod 

 shrimp {Penaeus foliaceus), from the calanoid whorled Channel copepod 

 plankton (Temora turhinaia), and the Atlantic copepod plankton crusta- 

 cean (Centropages typicus), and from other animal sources. Lowe and 

 Morton^" confirmed the results of Kaunitz and Slanetz^'*^ by proving that 

 a molecular distillate of lard, which was apparently free from vitamin A or 

 provitamin A, restored growth and cured xerophthalmia when given to vita- 

 min A-depleted rats at levels of 0.6 g./day; it was believed that these data 

 indicated the presence of a factor in lard capable of replacing vitamin A. 

 However, Herb, Riemenschneider, Kaunitz, and Slanetz^^ isolated frac- 

 tions from the molecular distillate which gave a positive Carr-Price reac- 

 tion and which exhibited a typical vitamin A-absorption curve. The con- 

 clusion of these authors that the biologic value of lard is actually attribut- 

 able to its vitamin A content seems entirely justified on the basis of their 

 data. The vitamin A-content is calculated to be 0.4 to 2.0 I.U./g. of the 

 distillate.851 



8« H. Kaunitz and C. A. Slanetz, Federation Proc, 9, 335 (1950). 



8" H. Kaunitz and C. A. Slanetz, /. Nutrition, 42, 375-389 (1950). 



8" L. Randoin and R. Netter, Compt. rend., 198, 2120-2122 (1934). 



8^* P. Dubouloz, R. Marville, and C. Chevalier, Bull. soc. chim. bioL, 30, 112-115 

 (1948). 



8« P. Le Gallic, Compt. rend. soc. bioL, I4I, 1214-1218 (1947); I42, 65-67 (1948). 



8" J. Mayer and W. A. Krehl, /. Nutrition, 35, 523-537 (1948). 



8« R. Grangaud and R. Massonet, Bull. soc. chim. biol, 31, 231-234 (1949). 



8« C. E. Lane, Science, 111, 471-472 (1950). 



850 J. S. Lowe and R. A. Morton, Biochem. J., 55, 681-686 (1953). 



85' S. F. Herb, R. W. Riemenschneider, H. Kaunitz, and C. A. Slanetz, J. Nutrition, 

 51, 393-402 (1953). 



