394 RIBOFLAVIN 



The effects of riboflavin derivatives on the growth of neoplasms have 

 been receiving increasing attention. Antopol and Unna^^ and Miller and 

 Miller^^ have shown that large amounts of riboflavin retarded the occur- 

 rence of pathological changes in liver produced by p-dimethylaminoazoben- 

 zene. Pollack et al.'^'^ noted that the concentration of riboflavin was lower 

 in tumor than in normal tissue. Severe riboflavin deficiency decreased the 

 growth rate of carcinomas^^ ■ *" in mice. This could be accomplished either 

 by riboflavin deprivation or by administering''- isoriboflavin or galactoflavin. 

 Diethyl-riboflavin^^ and 6,7-dichloro-9-(l'-D-sorbityl)isoalloxazine*^ were 

 effective in reducing the growth of tumors in rats. 



XII. Requirements and Factors Influencing Them 



M. K. HORWITT 



Any statement regarding the amount of riboflavin required must be a 

 compromise depending upon variations in the heredity, growth, environ- 

 ment, age, activity, and health of the organism. The synthesis of riboflavin 

 by the host and the differences in the availability of the vitamin from di- 

 verse sources must also be considered. With all these variables it is unlikely 

 that there will ever be complete agreement among the workers in this field. 

 Why, for example, only three out of fourteen men on identical diets low in 

 riboflavin,' living in the same environment for over a year, should show 

 relatively severe signs of ariboflavinosis, and why three others in the same 

 group should show no signs of deficiency at all, are questions which will 

 plague the investigator for years to come. The concept of "individual sus- 

 ceptibility" is an excuse which covers our ignorance and confounds those 

 responsible for statements of recommended allowances. 



A. OF ANIMALS 



Table III presents representative published requirements of some mam- 

 mals, birds, and fish. It is apparent from the data listed that there is not 



^^ W. Antopol and K. Unna, Cancer Research 2, 694 (1942). 



39 E. C. Miller and J. A. Miller, Cancer Research 7, 468 (1947). 



*" M. A. Pollack, A. Taylor, J. Taylor, and R. J. Williams, Cancer Research 2, 739 



(1942). 

 " H. P. Morris and W. van B. Robertson, J. Natl. Cancer Insi. 3, 479 (1943). 

 42 H. C. Stoerk and G. A. Emerson, Proc. Soc. Exptl. Biol. Med. 70, 703 (1943). 

 " H. V. Aposhian and J. P. Lambooy, Proc. Soc. Exptl. Biol. Med. 78, 197 (1951). 

 "4 F. W. Holly, E. W. Peel, R. Mozingo, and K. Folkers, /. .4m. Chem. Soc. 72, 5416 



(1950). 

 1 M. K. Horwitt, O. W. Hills, C. C. Harvey, E. Liehert, and D. L. Steinberg, /. 



Nutrition 39, 357 (1949). 



