XII. REQUIREMENTS AND FACTORS INFLUENCING THEM 295 



Be-deficient diet contaniiijj; 15% casein accelerated the deficiency and de- 

 creased survival time.'- When levels of methionine slightly greater than 

 that required for normal growth were fed to rats on a limiting amount of 

 \itamin Be, their growth rate was depressed; other amino acids had no 

 effect.'-" Cerecedo and Foy'^ have shown that weanling rats on a 60% 

 casein diet that was deficient in vitamin Be developed more severe skin 

 lesions earlier than did animals on a lower protein diet. These findings 

 suggest an inverse relationship between ^'itamin Be and protein intake. 

 The presence in the diet of unsaturated fat appears to spare pyridoxine.^^ 

 Suboptimal amounts of pyridoxine become optimal when supplemented 

 with linoleic acid-containing fats. 



Beaton et al}^"" have demonstrated the importance of other factors in 

 determining the severity of acrodynia in pyridoxine-deficient rats. Male 

 rats appeared to develop the deficiency with more rapidity and severity 

 than female rats, indicating a higher requirement for the former. When 

 the deficient diet contained an incomplete protein as the only source of 

 nitrogen, no acrodynia developed, suggesting that the skin lesions develop 

 under those dietary conditions which allow an increase in body weight 

 when the deficient diet is supplemented with vitamin Be . On the other 

 hand, the injection of growth hormone into pyridoxine-deficient animals 

 aggravated the deficiency symptoms. Adrenalectomy prevented the ap- 

 pearance of acrodynia in vitamin Be deficiency. 



AVhen rats are maintained at a temperature of 91°F. they require twice 

 the amount of pyridoxine necessary at 68°F.^^ 



2. Mice 



Young weanling mice on a pyridoxine-deficient diet containing 18 to 20 % 

 casein showed a good growth response when the diet was supplemented by 

 1 7 of pyridoxine per gram of diet.^^' ^^ When the deficient diet was sup- 

 plemented by only 0.5 7 of pyridoxine per gram of food, the animals grew 

 at one-half the normal rate. An increase in the protein level of the diet 

 elevated the requirement for vitamin Be. Deficient mice on a 60 % casein 

 level lived one-third as long as mice on a 10% casein diet; the mouse re- 

 quires three times as much pyridoxine on a diet of 00 % casein than when 

 20 % was fed. i.-Tryptophan administration decreased the survival time of 



'= L. R. Cerecedo, J. R. Foy, and E. C. De Renzo, Arch. Biochem. 17, 397 (1948). 



'2" II. .]. DeBey, E. E. Snell, and C. A. Baumaiin, ./. Nutrition 46, 203 (1952). 



" L. R. Cerecedo and J. R. Foy, Arch. Biochem. 5, 207 (1944). 



'^ II. Sherman, Vitamins and Hormones 8, 55 (1951). 



"" J. R. Beaton, J. L. Beare, and E. W. MoIIenry, ,/. Nntritinn 48, 325 (1952). 



'^ ('. A. Mills, Arch. Biochem. 1, 73 (1942). 



""' K. C. Miller and C. A. liaumann, ./. Biol. ('hem. 157, 551 (1945). 



'~ II. P. Morris, Mtatnin.'^ and Hormones 5, 175 (1947). 



