Effect of Tryptophan Deficiency on the Urinary Excretion of Tryptophan and Niacin Metabolites in Rats

Abstract

The effect of tryptophan deficiency on the urinary excretion of tryptophan and niacin metabolites and riboflavin, and on nitrogen balance has been examined in rats. The excretion of xanthurenic acid decreases, and the excretion of N1 -methylnicotinamide (MNA) slightly increases when tryptophan is def icient. But the increase in MNA excretion was not statistically signi ficant, perhaps owing to the scatter of the data. Decrease in the excretion of N-methyl-2-pyridone-5-carboxamide (pyridone) is as low as 1/2 to 1/20 of the control level when tryptophan is deficient. The excretion of riboflavin increases when tryptophan is deficient.