294 PYRIDOXINE AND RELATED COMPOUNDS 



threefold function in the body, it is conceivable that the requirement for 

 one function may not be the same as for the other functions. Many times, 

 growth is used as the criterion of response, but, since this is not specific, it 

 may not be the appropriate criterion to employ; in a deficiency, biochemical 

 systems which require vitamin Be may cease to function long before growth 

 is affected. The synthesis of vitamin Be by intestinal bacteria also compli- 

 cates this entire requirement picture. 



1, Rats 



The majority of investigators have advocated a pyridoxine requirement 

 of 10 7 per day or 100 y per 100 g. of diet for normal growth.^ This value 

 also applies to the requirement of the cotton rat (Sigmodon hispidus hispi- 

 dus)} During lactation, however, this amount is increased to 120 to 200 

 7 per 100 g. of ration.^ The vitamin Be reciuirement can also be increased 

 by inducing an experimental hyperthyroidism^ and by overloading the diet 

 with thiamine.^ The vitamin Be requirement does not appear to be increased 

 in aging rats; thiamine requirement, however, is increased.^ 



The three active forms of the vitamin Be complex are equally effective in 

 promoting growth and in curing acrodynia when fed by medicine dropper 

 or injected interperitoneally;^ however, when added to the diet, pyridoxine 

 seems to be the most active. It has been suggested that intestinal micro- 

 organisms utilize or destroy pyridoxal and pyridoxamine preferentially. 

 Links wiler et al} have shown that aureomycin increased the growth of rats 

 fed limiting levels of pyridoxine, pyridoxal, or pyridoxamine. These three 

 forms, however, were equally active in promoting growth when fed in the 

 diet with aureomycin. The authors postulate that the antibiotic may pre- 

 vent utilization or destruction of the vitamin Be group by intestinal micro- 

 organisms, thus increasing the amount available to the rat. 



The vitamin Be requirement also appears to be influenced by the quali- 

 tative and quantitative amino acid composition of the diet. The feeding of 

 large amounts of DL-serine^ or glycine^"' " to rats increases their vitamin Be 

 requirement. The addition of cystine or methionine to rats fed a vitamin 



1 R. A. Brown and M. Sturtevant, Vitamins and Hormones 7, 171 (1949). 



2 B. S. Schweigert, Vitamins and Hormones 6, 55 (1948). 



3 C. A. Slanetz, Am. J. Vet. Research 4, 182 (1943). 



4 V. A. Drill and R. R. Overman, Am. J. Physiol. 135, 474 (1942). 



5 M. B. Richards, Brit. Med. J. 1, 433 (1945). 

 « C. A. Mills, Am.. ./. I'hi/.^iol. 153, 31 (1948). 



7 P. S. Sarma, E. E. Snell, and C. A. Elvehjem, J. Biol. Chcm. 165, 55 (1946). 



8 H. Linkswiler, C. A. Baumann, and E. E. Snell, J. Nutrition 43, 565 (1951). 

 '■> W. II. Fishman and C. Artom, Proc. Soc. Exptl. Biol. Med. 57, 241 (1944). 



'» E. Pag^ and R. Gingras, Trans. Roy Soc. Can. 40, 119 (1946). 

 '1 E. PagC; and R. Cingras, Rev. can. hiol. 6, 372 (1947). 



