Metabolism of ^<57>Co-Methylcobalamin in Rat and Guinea Pig

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The metabolic fate of ^<57>Co-methylcobalamin after oral or intraperitoneal administration to rats and guinea pigs (25 μg/kg) have been studied. From fecal excretion test, the intestinal absorption of ^<57>Co-methylcobalamin seems to be less than 5% of dose and the time course of fecal excretion was differed in both species. The fecal excretion in guinea pig was slower and more continuous than in rat. The urinary excretion of radioactivity after intraperitoneal administration was lower in rat (41% of dose during the first 24 hr) than in guinea pig (68%) and the main excretion form in urine was ^<57>Co-methylcobalamin itself in both species. ^<57>Co-methylcobalamin might be stable in intestinal tract and transfered through intestinal wall in unchanged form. Tissue distribution of radioactivity after intraperitoneal administration was higher in rat than in guinea pig generally and the highest uptake in rat was found in kidney, while the trend of higher uptake in guinea pig was found in liver. The biological conversion of ^<57>Co-methylcobalamin incorporated in liver and kidney into other cobamide analogues has been studied and it has been evident that ^<57>Co-methylcobalamin was transformed to 5,6-dimethylbenzimidazolylcobamide coenzyme and hydroxocobalamin in both species.
公益社団法人日本薬学会の論文
1972-12-25