Abstract
Male rats of Sprague Dawley strain (5-week old) were divided into four groups and then fed thiamin-free, thiamin-free + 1% nicotinamide, normal (thiamin-free diet+0.59 mg%thiamin hydrochloride) and the normal + 1% nicotinamide diets for 24-29 days. Tryptophan metabolites in the liver, blood and urine, thiamin in the liver and urine and enzyme activities of tryptophan-NAD pathway and of transketolase were compared among the four groups. NAD level in the blood and liver was almost the same between the normal and the thiamin-free groups, while that in the group of the normal+nicotinamide diet was much higher than that in the group of the thiamin-free+nicotinamide diet. The activity of liver nicotinamide methyltransferase and amount of N^1- methylnicotinamide in both thiamin-free groups were significantly increased in comparison with those in both normal groups. Urinary thiamin excretion was significantly higher in the thiamin-free+nicotinamide group than in the thiamin-free group. The same relation of thiamin excretion was also observed between the groups of the normal and normal+nicotinamide.
