Effect of Dietary Protein Levels on the Urinary Excretion of Nicotinamide and Its Metabolites in Rats

Tissue vitamin concentrations are maintained constant by changing the urinary excretion rate of vitamins in rats’ restricted food intake

“…Under ad libitum feeding conditions, these percentages for vitamin B 1 , vitamin B 2 , vitamin B 6 , vitamin B 12 , pantothenic acid, folate, and biotin were about 16, 32, 44, 18, 62, 7, and 23%, respectively. The percentage of excretion of niacin compared with intake of niacin could not be calculated because nicotinamide is biosynthesized from tryptophan, and the conversion percentage is known to be affected by many factors such as energy restriction, 7) starvation, 8) protein intake, 25) and the amino-acid composition. 26) The urinary excretion percentages of vitamins over the intakes were observed some characteristic phenomena.…”

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

“…Shibata and co-workers 10,[17][18][19][20][21][22]33) found that the urinary excretory ratio of (2-Py + 4-Py)/MNA primarily reflected protein nutritional status, not Nam nutritional status, because the excretory ratio was decreased by the administration of an extremely large amount of Nam 34) and MNA 35) in rats. In addition, Shibata et al 36) reported that the administration of 150 mg/d of Nam did not affect the excretory ratio in humans.…”

“…[11][12][13][14][15] Krehl et al 16) found that Trp could completely counteract the growth retardation caused by corn grits diet in rats. The conversion ratio of Trp to Nam is not constant: It is affected by age, 5) various nutritional factors, 10,[17][18][19][20][21][22][23][24][25] hormones, [26][27][28] and chemicals. [29][30][31] Therefore, it is important in preventing a pellagra outbreak to know the conversion ratio of Trp to Nam under the conditions, but it is not possible to know this in case of emergency and conflict.…”

Inhibition ofN1-Methylnicotinamide Oxidase Activity by a Large Nicotinamide Injection into Rats

“…the MNA excretion, being ten-fold higher than in the 2-py excretion, and the MNA excretion is two-fold higher than the 2-py excretion. 4 ) Therefore, it is probable that the activities of 2-py and 4-py forming enzymes are inhibited by a pharmacological dose of Nam and that the inhibition is higher in the 4-py formation than in the 2-py formation. This experiment was done to demonstrate this probability and to investigate how long the changed ratios of 4-py to 2-py and 2-py plus 4-py to MNA excretion continue.…”