Effect of Pyridoxal on the Urinary Excretion of Nicotinamide Metabolites in Rats(Biological Chemistry)

概要

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The effects of pyridoxal on the urinary excretion of nicotinamide metabolites such as N^1-methylnicotinamide (MNA), N^1-methyl-2-pyridone-5-carboxamide (2-Py), and N^1-methyl-4-pyridone-3-carboxamide (4-Py) were investigated. When a pharmacological amount of pyridoxal (500μmol/rat) was intraperitoneally injected into rats, the MNA excretion from 0 to 5 hr urine after the injection increased 5-fold, and concomitantly, the 2-Py excretion decreased by 1/2 and 4-Py excretion by 1/3. Therefore, the ratio of (2-Py + 4-Py) to MNA excretion was decreased greatly (1/15) by pyridoxal loading. These changes were gone by the 5-10 hr urine after the injection. In order to investigate these changes, the rats were killed 2 hr after the pyridoxal injection, and the activities of liver nicotinamide methyltransferase, 2-Py-forming MNA oxidase, and 4-Py-forming MNA oxidase were measured. Nicotinamide methyltransferase activity was increased slightly by the pyridoxal loading, but, 2-Py-forming MNA oxidase and 4-Py-forming MNA oxidase activity decreased greatly. Therefore, it was found that the increase in the urinary excretion of MNA and the concomitant decrease in the urinary excretion of 2-Py and 4-Py might be due to the inhibition of 2-Py-forming MNA oxidase and 4-Py-forming MNA oxidase activities by the pyridoxal loading.
社団法人日本農芸化学会の論文
1990-03-23