NICOTINIC ACID (NIACIN) 



from blacktongue exhibited dehydration and electrolyte imbalance ; ' 

 these symptoms were alleviated and life was prolonged by feeding 

 sodium chloride, but nicotinic acid deficiency eventually supervened. 

 This was characterised by a lowered content of glucose and chloride 

 in the blood and by a low carbon dioxide-combining capacity of the 

 blood. The plasma protein and non-protein nitrogen were high. 

 These changes were reversed on administration of nicotinic acid. 

 Nicotinic acid deficiency also resulted in the appearance of a severe 

 macrocytic anaemia, which was not alleviated by iron, protein, 

 glucose, haemoglobin, xanthopterin, the anti-pernicious anaemia 

 factor or cobalt.® The reticulocyte coimt rapidly increased on ad- 

 ministration of nicotinic acid or nicotinamide, unless the deficiency 

 was severe ; in this event, folic acid relieved the symptoms.^ Folic 

 acid prevented the development of symptoms of blacktongue, suggest- 

 ing that some connection exists between folic acid and nicotinic acid. 



Other Animals 



Nicotinic acid is also essential for pigs,^° monkeys ^^ and rabbits. ^^ 

 On a high protein diet, pigs failed to exhibit symptoms of nicotinic 

 acid deficiency, but on a diet low in protein, impaired growth, rough 

 coats, diarrhoea, poor appetite and severe anaemia were observed in 

 the absence of nicotinic acid.^^ The protective effect of protein was 

 presumably due to its tryptophan content (see page 242). Nicotinic 

 acid-deficient pigs responded to tryptophan equally as well as to 

 nicotinic acid.^* 



Monkeys fed a purified diet low in nicotinic acid developed a 

 deficiency syndrome characterised by loss in weight, anorexia and low 

 haemoglobin.^^ The animals also failed to grow on a diet containing 

 40 % of corn grits ; the haemoglobin was again suboptimal and a 

 reversed neutrophil-lymphocyte count occurred. In neither instance 

 were the symptoms cured by nicotinamide, but whole liver effected a 

 complete cure. 



Rabbits on a nicotinic acid-deficient diet lost weight and developed 

 anorexia and diarrhoea,^^ ^^^ the diarrhoea was probably due to 

 inanition, rather than to the absence of nicotinic acid per se. After 

 eight weeks on a deficient diet the haemoglobin and cellular com- 

 ponents of the blood were reduced, and after twelve weeks the nico- 

 tinic acid content of the tissues was markedly reduced. ^^ The 

 symptoms were cured by administration of either 400 mg. of DL- 

 tryptophan or 10 mg. of nicotinic acid per kg. of bodyweight, the 

 response to each being approximately equal. The only difference be- 

 tween the two was that the nicotinic acid content of the muscles was 

 increased when nicotinic acid, but not tryptophan, was administered. 



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