IV. BIOCHEMIC.\L SYSTEMS 



515 



of nicotinic acid in man and eight other mammahan species and have re- 

 viewed much of the earher work on this subject. Table X has been adapted 

 from their data to indicate the marked species variation. Apparently, man, 

 dog, rat, and swine dispose of nicotinic acid largely as methylated products, 

 whereas the herbivora, rabbits, guinea pigs, sheep, goats, and calves, dis- 

 pose of nicotinic acid in some other fashion. Johnson et al}^'' also found that 

 nicotinic acid was excreted principally in a methylated form in human 

 subjects. Ellinger and associates^^^ have studied this question extensively 

 in man, dog, cat, rat, rabbit, and guinea pig. They obtained results es- 

 sentially the same as Perlzweig et alP^ with reference to the ability of 



TABLE X 

 Urinary Excretion op Nicotinic Acid and Its Derivatives 



" N'-Metliylnicutinamide. 



* 6-Pyridone of N'-methylnicotinamide. 



'^ Includes nicotinic acid, nicotinamide, and nicotinuric acid, if present. 



* Tlie significance of these values below 1% is questionable owing to analytical limitations. 

 ^ Nicotinic acid content estimated at 17 mg. 



various species to excrete methylated derivatives of nicotinic acid. The cat 

 resembles other carnivorous and omnivorous species in that it does ex- 

 crete N'-methylnicotinamide. Chickens excrete a still different type of 

 nicotinic acid derivative — dinicotinylornithine.'^^ N'-Methylnicotinamide is 

 not a major urinary product in the horse,^""' ^"^ although it is in the cotton 

 rat.^oi 



The biochemical mechanisms by which the urinary derivatives of nico- 



'" B. C. Johnson, T. S. Hamilton, and H. H. Mitchell, J. Biol. Chem. 159, 231 (1945). 

 '98 P. Ellinger and M. M. Abdel Kader, Biochem. J. 44, 77, 627 (1949). 

 '9' W. J. Dann and J. W. Huff, J. Biol. Chem. 168, 121 (1947). 

 ^o" J. W. Huff, P. B. Pearson, and W. A. Perlzweig, Arch. Biochem. 3, 99 (1946). 

 20' B. S. Schweigert, P. B. Pearson, and M. C. Wilkening, Arch. Biochem. 12, 139 

 (1947). 



