Vitamin B12 Biosynthesis after Oral and Intravenous Administration of Inorganic Co60 to Sheep.

Abstract

1. Excretions and tissues from wether lambs dosed orally and intravenously with inorganic cobalt-60 were measured for total radioactivity and also for radioactivity in fractions characterized chemically as vit. B₁₂-like, inorganic and bound. 2. After oral administration there was considerable biosynthesis of vit. B₁₂ in the tract, probably occurring mainly in the rumen. After intravenous administration there was only slight, if any, biosynthesis in the tract, but considerable formation of vit. B₁₂ in the tissues with the suggestion that the adrenals and spleen were mainly responsible. Overall, there was more than 10 times as much Co⁶⁰ converted to B₁₂ after ingestion than after intravenous administration. 3. The concentrations of vit. B₁₂-like Co⁶⁰ in the tissues after intravenous injection were slightly higher than after ingestion of equal amounts of Co⁶⁰. 4. In the light of results on the response of cobalt-deficient lambs to parenterally administered vit. B₁₂, it is suggested that the vit. B₁₂-like material synthesized by the tissues from inorganic cobalt is physiologically ineffective in relieving cobalt-deficiency symptoms in sheep.