XI. I'll AKM ACOI.OCY 291 



l'\ ri(lo\;in\iii(' has Ixmmi IoiiikI Io pirxciit lalal <()ii\ ulsioiis caused liy 

 tlii()S(Mui('ail»a/.i(lt' in mice; intraperitoneal inject ions ot 'A'lO in<i. per kilo- 

 gram preredint;- a ihrcH'I'old lellial d()S(> of thioseinicarltazidc j)re\'en(ed all 

 toxic nianit'estalions.' IVridoxine and pyridoxal were said to he less elleclivc 

 antidotes, 'i'oxic effects of seinicarhazide were less readily luitagonizod by 

 pyridoxaniine. In mice and rats, pyi'idoxine in doses of (> mg. to SOO mj;". 

 ])(>r kilofii'am raised the comiilsive doses of semicar))azide sif2;nificantly; 

 intra \-enous injections of 100 to 400 m<i;. picNcnted semicarhazide seizures 

 in man.-' On the other hand, pyridoxine failed to exert an anticonvulsant 

 etiect against seizures induced by metrazol, strychnine, ammonium acetate, 

 or by electroshock in mice^ and b\^ electroshock in rats.® 



Pyridoxine, in eonjunotion with other B vitamins, may also eounteract 

 the anorexia and anemia caused by promin in rats.'^ 



Pyridoxine has been stated to protect mice from death by x-ray radia- 

 tion, although the leucopenia was not influenced; a similar protection was 

 obtained with folic acid.^ On the other hand, a protective effect of pyri- 

 doxine against injurious effects of P'- could be demon.strated only in pyri- 

 doxine-deficient mice but not in normal mice.^ 



Toxic effects of desoxypyridoxine in chicks,'" in rats,"- '- and in man'-' 

 are readily explained by its conversion into desoxypyridine phosphate and 

 subsequent competition with pyridoxal phosphate for the apoenzyme.'"* 

 The toxic effects of desoxypyridoxine resembling the manifestations of 

 pyridoxine deficiency were readily obtained when the diet was restricted in 

 pyridoxine. On an adequate intake of pyridoxine, toxic effects occurred in 

 rats only after the diet was supplemented with 50 mg. % of desoxypyri- 

 doxine;'- intramuscular injection of 50 mg. caused no ill effects in normal 

 man.'^ 



Pyridoxine is readily absorl)ed from the gastrointestinal tract and rapidly 

 metabolized. Only small fractions of ingested or injected pyridoxine arc 

 excreted as such in the urine. In normal persons on adecjuate diets a pyri- 

 doxine activity corresponding to less than 1 jug. per milliliter was found in 

 the urine.' After intravenous administration of 50 to 100 mg., only 5 to 10 % 



5 E. H. Jenney, R. P. Smith, and C. C. PfeifTer, Federation Proc. 12, 333 (1953). 



6 V. D. Davenport and H. W. Davenport, J. Nutrition 36, 139 (1948). 



7 G. M. Higgins, Am. J. Med. Sci. 207, 239 (1944). 



8 A. Goldfeder, L. Cohen, C. Miller, and M. Singer, Proc. Sac. Exptl. Biol. Med. 67, 

 272 (1948). 



9 C. Artom, W. E. Cornatzer, and G. T. Harrell, Proc. Soc. Exptl. Biol. Med. 79, 494 

 (1952). 



'» W. H. Ott, Proc. Soc. Exptl. Biol. Med. 61, 125 (1946). 



" C. C. Porter, I. Clark, and R. H. Silher, /. Biol. Chem. 167, 573 (1947). 



'2 G. A. Emerson, Federation Proc. 6, 406 (1947). 



" J. F. Mueller and R. W. Vilter, J. Clin. Invest. 29, 193 (1950). 



'* W. W. Umbreit and J. G. Waddell, Proc. Soc. Exptl. Biol. Med. 70, 293 (1949). 



