METABOLISM 



other four species, deaminated nicotinamide. When rabbits were 

 given a meat-bread diet in place of a diet of cabbage or oats, the 

 methylating mechanism was suppressed completely and the de- 

 aminating mechanism partially. 



Follo^^dng oral or subcutaneous administration of 2 g. of nicotin- 

 amide daily for three days, goats, sheep and calves excreted slightly 

 more N^-methylnicotinamide than usual ; goats and sheep also 

 excreted slightly more Ni-methyl-6-pyridone-3-carboxylamide, but no 

 measurable amount was excreted by calves. ^^^ 



Assessment of Nutritional Status 



It has been pointed out above (page 257)* that the excretion of 

 N^-methylnicotinamide by subjects given an unsupplemented diet 

 cannot be used to measure nutritional status. More promising results 

 were obtained when the increased excretion of N^-methylnicotinamide 

 and other metabolites of nicotinic acid was estimated, following the 

 administration of a test dose of nicotinic acid or nicotinamide. G. A. 

 Goldsmith ^® found that normal subjects given a 300-mg. dose of nico- 

 tinamide by mouth excreted twice as much trigonelline (this would 

 also have included any N^-methylnicotinamide) as hospital patients 

 given the same treatment, whilst patients with pellagra or vitamin B 

 complex deficiency excreted still less. He suggested that measure- 

 ment of the nicotinic acid derivatives excreted within six hours of 

 administering a 300-mg. test dose of nicotinamide orally was a useful 

 indication of nutritional status. 



Perlzweig et al.^^ found that excretion of both trigonelline and 

 nicotinic acid was increased after intravenous injection of a 500-mg. 

 dose of nicotinamide. " Normal " subjects, however, showed a 

 lower excretion than did hospital patients, presimiably because in 

 this instance the latter were the more saturated with respect to nico- 

 tinic acid. The urinary excretion of nicotinic acid after a test dose 

 was much less in pellagrins than in controls,^^ and the response to a 

 test dose was said to be a better criterion of nicotinic acid deficiency 

 than a low blood level. 



According to P. Ellinger and R. A. Coulson,^^ from 2 to 8 mg. of 

 N^-methylnicotinamide are eliminated daily in the urine, and this is 

 increased by the ingestion of additional nicotinamide or nicotinic 

 acid, though significant amounts are stored in the body. They 

 found that the elimination curve was constant for different individuals 

 but that the height of the curve depended on the dietary intake and 

 on the efficiency of the methylation mechanism of the body. They 

 suggested that N^-methylnicotinamide was not the final metabolite, 

 but that this was converted into other products not yet identified. 



259 



