The Urinary Excretory Ratio of Nicotinamide Catabolites Was Associated with the Conversion Ratio of Tryptophan to Nicotinamide in Growing Rats Fed a Niacin-Free 20% Casein Diet

Abstract

Weaning rats were fed a niacin-free 20% casein diet. Twenty-four-h-urine samples were collected, and nicotinamide and its catabolites were measured. A correlation was found between the urinary excretory ratio of nicotinamide catabolites (N¹-methyl-2-pyridone-5-carboxamide + N¹-methyl-4-pyridone-3-carboxamide)/N¹-methylnicotinamide and the tryptophan-nicotinamide conversion ratio during growing period of the rats. This indicates the possibility that the conversion ratio can be deduced from the excretory ratio.