ANALOGUES 

 CHjOH 

 /^COOH 

 CH3 



V 



Growth Inhibitors 



The first substance related to pyridoxine which was found to have 

 inhibitory properties was 3-hydroxy-5-hydroxymethyl-2 : 4-dimethyl- 

 pyridine, generally referred to as desoxypyridoxine (page 343) 



CH, 

 Ho/^jCHaOH 



W. H. Ott 21 showed that two moles of this substance antagonised 

 the effect of one mole of pyridoxine in chicks, producing symptoms of 

 vitamin Bg deficiency. Normal rats receiving desoxypyridoxine 

 along with tryptophan excreted more xanthurenic acid and kynurenine 

 (page 336) than animals receiving tryptophan alone, whilst vitamin 

 Bg-deficient rats excreted even larger amounts of xanthurenic acid 

 and kynurenine in presence of the ant i- vitamin. 22 The administration 

 of pyridoxine reduced the excretion of these two substances to normal 

 levels. It was suggested that desoxypyridoxine interfered with some 

 phase of tryptophan metabolism. Other symptoms consistent with 

 P3n:idoxine deficiency were observed in chicks, dogs and monkeys to 

 which desoxypyridoxine was administered. ^^ Desoxypyridoxine ad- 

 ministered to female rats ten to twenty days prior to mating inter- 

 fered with reproduction, the effect being counteracted by pyridoxine 

 given on the day of mating. ^^a Desoxypyridoxine (i mg.) injected 

 into eggs just prior to incubation resulted in 100 % mortality ; this 

 was prevented by simultaneous injection of any of the three forms of 

 vitamin Bq.^^^ 



Desoxypyridoxine did not inhibit the action of tyrosine decarboxyl- 

 ase, but phosphorylated desoxypyridoxine displaced pyridoxal phos- 

 phate in the tjnrosine decarboxylase system. 2* Administration of 

 desoxypyridoxine produced marked regression of lymphosarcoma 

 implants in mice, but not when pyridoxine was added to the diet.^^ 

 Tumour implants failed to develop in animals deprived of pyridoxine 

 prior to the implantation. Desoxypyridoxine inhibited the multipli- 

 cation of T2r+ E. coli bacteriophage and the inhibition was reversed 

 by pyridoxine. 25« 



Another substance with anti-pyridoxine activity is 3-hydroxy- 

 5-hydroxymethyl-4-methoxymethyl-2-methyl-pyridine often, though 



345 



