Metabolic fate of nicotinamide in LEC rats.

Metabolic fates of nicotinamide in Wistar and LEC rats were compared. In Wistar rats (normal rats) nicotinamide was generally catabolized to N1-methyl-4-pyridone-3-carboxamide (4-Py) through N1-methylnicotinamide (MNA). But in LEC rats nicotinamide catabolism mainly stopped at MNA. Therefore, the excretion ratio of (N1-methyl-2-pyridone-5-carboxamide + 4-Py)/MNA, which is an index of amino acid adequacy, was much lower in the LEC rats than in the Wistar rats. This phenomenon was attributed to the fact that the 4-Py-forming MNA oxidase activity was much lower in the LEC rats than in the Wistar rats. The NAD contents in liver and blood were also lower in LEC rats than in Wistar rats. These results suggest that the ability to synthesize proteins such as 4-Py-forming MNA oxidase and dehydrogenases may be impaired in LEC rats.