ラットのNicotinamide腹腔内投与によるN'-Methylnicotinamideの尿中排泄

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It is well known that a large dose injection of nicotinamide caused a striking rise in liver NAD in rats as well as in liver nicotinamide. Consequently, the vitamin and its metabolites were excreted in the urine, especially relatively large amounts of N'-methylnicotinamide (MNA) which is normally arised from nicotinamide resulting in breakdown of NAD in the liver. In order to know the origins of urinary MNA, female rats were given nicotinamide (500 mg/kg body weight) intraperitoneally. The time course of urinary excretion of nicotinamide and MNA was studied on the urine collected with a small glass catheter inserted into urethra and it was compared with the hepatic contents of nicotinamide and NAD with time. Urinary excretion of nicotinamide showed a maximal peak at 2 hours after administration and then it rapidly decreased. This excretory pattern reflected the hepatic content levels of nicotinamide which reached the maximum immediately after its administration, and reduced repidly. On the contrary, significant amounts of MNA were excreted at later time periods ; its excretion increased slowly and almost linearly upto 10 hours after administration and its maximal level continued for 8〜10 hours. This finding of MNA excretion corresponds closely to the change of liver NAD contents which were gradually increased and began to drop at 8 hours after administration of nicotinamide. These results suggest that nicotinamide administered in a large amount was hardly methylated directly for the formation of MNA during the early period and that after once synthesized to the hepatic NAD, it was excreted as substrate for the formation of MNA over the later period.
日本ビタミン学会の論文
1973-08-25

ラットのNicotinamide腹腔内投与によるN'-Methylnicotinamideの尿中排泄

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