NICOTINIC ACID (nIACIN) 



(One of these is presumably N^-methyl-6-pyridone-3-carboxylamid.e, 

 page 255). This view is also supported by the findings of W. A. 

 Perlzweig and J. W. Huff ^^ referred to above. 



Similar saturation tests were used by several other workers ;33-36 

 in these the amount of N^-methylnicotinamide excreted in the urine 

 in response to nicotinamide orally administered was measured. Sub- 

 stantially lower excretions were observed in pellagrins than in healthy 

 subjects,^^' ^^» ^^' ^^ e.g. deficient subjects excreted up to 5 % only of 

 the test dose compared with 8 to 25 % excreted by controls. The 

 excretion of acid-hydrolysable nicotinic acid derivatives in normal 

 subjects is remarkably constant and no significant difference was 

 observed in the output of non-pregnant women and women in early 

 pregnancy.^^" In the last trimester of pregnancy, however, the 

 amount excreted increased significantly and so did the proportion of 

 a 50-mg. test dose that was eliminated, suggesting that the maternal 

 organism requires additional coenzymes I and II in the last three 

 months of pregnancy and that during this period there is a greater 

 turnover of coenzymes. 



Not only may the extent to which N^-methylnicotin amide is elim- 

 inated be influenced by the efficiency of the methylating mechanism, 

 but it will also depend on the efficiency of absorption from the intes- 

 tine.^^' ^^ This second factor affects the response in pellagrins but 

 not in healthy persons. A third factor that may influence nicotin- 

 amide saturation tests is the presence of bacteria in the intestine that 

 either synthesise,^^' 3^» *^' ^^ or destroy,*^' ^^ nicotinamide. 



A critical study of the effect of methionine on the nicotinamide 

 saturation test was undertaken by P. Ellinger and S. W. Hardwick,*^ 

 who demonstrated that the test previously proposed by them ^^ 

 might be affected by exhaustion of the methyl donators of the body 

 and therefore not provide a true picture of nicotinamide status. It 

 was found, for instance, that methionine gave a greater response 

 after ingestion of 500 mg. of nicotinamide than after ingestion of 100 

 mg. Accordingly the test was modified, the amount of N^-methylnico- 

 tinamide excreted in the urine being estimated each day for eighteen 

 days ; immediately after the third, sixth, ninth and twelfth collec- 

 tions, 100 mg. of nicotinamide were administered, subcutaneously on 

 the first and last, orally on the second and rectally on the third occasion. 

 The percentage recovery of ingested nicotinamide was calculated for 

 a twenty-four-hour and a seventy-two-hour period. Three pellagrins 

 gave a response of 3-28 mg. and 5-35 mg. after twenty- four and seventy- 

 two hours, whilst healthy subjects gave 8-i8 and 9-96 mg. respectively. 

 It was impossible to account for all the nicotinamide administered. 



N^-Methylnicotinamide was excreted by newborn and premature 

 infants following the administration of nicotinamide, nicotinic acid 



260 



