PHARMACOLOGY 



human requirements there is the added difficulty that pyridoxine 

 deficiency does not result in the development of characteristic symptoms 

 that can be used as a criterion of response. 



The quantity of pyridoxine required to produce normal growth in 

 the rat was found to be lo ^g. per day ; up to loo fig. were required 

 to cure symptoms of vitamin Bg deficiency.^ When maintained at a 

 temperature of gi° F., rats required twice the amount of pyridoxine 

 found to be necessary at 68° F., whilst chicks maintained at 91° F. 

 required four times the amount necessary at 70° F.^ Lactating rats 

 required at least 50 fig. of pyridoxine per day to ensure that their 

 offspring did not suffer from spontaneous seizures and at least 150 

 /xg. per day to afford protection against artificially induced seizures. 



Symptoms of vitamin Bg deficiency in young turkeys ^ and 

 ducklings * were prevented by 3-0 and 2-5 mg. of pyridoxine per kg. 

 of diet respectively. 



References to Section 13 



1. E. J. Reedman, W. L. Sampson and K. Unna, Proc. Soc. Exp. Biol. 



Med., 1940, 43, 112. 



2. C. A. Mills, Arch. Biochem., 1942, i, 73. 



3. F. H. Bird, F. H. Kratzer, V. S. Asmundson and S. Lepkovsky, 



Proc. Soc. Exp. Biol. Med., 1943, 52, 44. 



4. D. M. Hegsted and M. N. Rao, /. Nutrition, 1945, 30, 367. 



14. PHARMACOLOGY OF PYRTOOXINE 



According to K. Unna and W. Antopol/ the toxicities (LD50) of 

 pyridoxine and its hydrochloride are 3-1 and 37 g. per kg. of body- 

 weight respectively when given subcutaneously to rats, and 4 and 6 g. 

 per kg. when given orally. According to Weigand et al.,^ the LD50 

 of pyridoxine by the intravenous route was 18-3 mg. per kg. for rats 

 and 42-9 mg. per kg. for mice ; 200 mg. were non-toxic in man. 



Dogs given 20 mg. per kg. orally for seventy-five days, and monkeys 

 given 10 mg. per kg. orally for thirty-nine days and subcutaneously 

 for loi days, suffered no ill-effects.^ 



A solution containing one part of pyridoxine hydrochloride in 

 8000 caused only a brief inhibition of the movements of the isolated 

 rabbit's gut, but caused a lasting contraction of the guinea-pig uterus. 2 

 In a concentration of 0-0005 millimoles per litre, pyridoxine hydro- 

 chloride significantly increased the work output of perfused frog's 

 muscle,^ and the improvement was maintained when the concentra- 

 tion was increased ten-fold. Above this level, however, no further 

 improvement occurred. 



329 



