Tissue Distribution and Storage Forms of Vitamin B 12 Injected and Orally Administered to the Dog. ∗

Abstract

Summary

1. The distribution of oral and intravenous Vit. B₁₂ was determined simultaneously in dogs using vitamin preparations labeled respectively with cobalt-57 and cobalt-60. 2. Thirty-one days after administration, the ratio of Co⁵⁷/Co⁶⁰ was constant in all tissues, indicating the existence of a common pool for cobalamin and related compounds regardless of mode of administration. 3. Conversion of administered labeled Vit. B₁₂ to a noncyano form was demonstrated by reverse isotope dilution analysis of livers. This is true regardless of mode of administration. 4. It is suggested that chemical changes in the vitamin account in part for the complex excretion pattern of labeled Vit. B₁₂.