Metabolic Fate of ⁵⁷Co-Labeled Hydroxocobalamin and ⁵⁷Co-Labeled 5, 6-Dimethylbenzimidazolylcobamide Coenzyme in Rats

Abstract

The metabolic fate of ⁵⁷Co-hydroxocobalamin (⁵⁷Co-OH-B₁₂) and ⁵⁷Co-5, 6-dimethyl-benzimidazolylcobamide coenzyme (⁵⁷Co-DBCC) has been studied after intraperitoneal administration at the dosage of 25 μg/kg in rats. About 60% of radioactivity administered was recovered in urine during the first 24 hr after administration of ⁵⁷Co-OH-B₁₂ or ⁵⁷Co-DBCC. The highest tissue uptake was found in kidney, especially after injection of ⁵⁷Co-DBCC, followed by adrenal gland, pancreas, stomach and liver. The distribution in brain, muscle and adipose tissue was much lower. It is evident that ⁵⁷Co-OH-B₁₂ was converted to ⁵⁷Co-DBCC and reverse conversion of ⁵⁷Co-DBCC occured in liver and kidney. Furthermore, ⁵⁷Co-methylcobalamin (⁵⁷Co-CH₃-B₁₂) was found to be yielded from both the cobamides. The biological interconversion among ⁵⁷Co-CH₃-B₁₂, ⁵⁷Co-OH-B₁₂and ⁵⁷Co-DBCC was established.