Abstract
The metabolic fate of 57Co-labeled methylcobalamin (57Co-CH3-B12) at various doses (5, 50 and 500 μg/kg/day) after consecutive, intraperitoneal administration within 7 days to rats, of which the right sciatic nerve was degenerated by crushing, was studied. The uptake of radioactivity by sciatic nerve in both sides was increased with time and doses but the radioactivities in sciatic nerve and muscles innervated by this nerve such as musculus gastrocnemius were significantly higher in crushed side than in intact one at all doses investigated. The distribution of radioactivity in tissues other than nerve and muscles was also increased with time and doses. The highest uptake was observed in kidney, followed by adrenal gland, pancreas and liver and the lowest in brain and testis. The urinary excretion of radioactivity in each dosage within 24 hr after every administration of 57Co-CH3-B12 was found to be nearly constant at each dose during 7 days, namely, about 25, 70 and 75%/day at 5, 50 and 500 μg/kg/day, respectively.
