Gastrointestinal Absorption and Urinary Excretion of Vitamin B12-Co60.

Abstract

The urinary and fecal excretion of radioactive material following oral doses of less than 1.0 [mu]g of vitamin B12-Co60 was utilized as an assay of intrinsic factor and depends upon a constant bond between vitamin B12 and Co60. Radioactive material obtained from the urine of normal patients following an oral dose of vitamin B12-Co60 plus a subcutaneous dose of 1000 [mu]g of nonradioactive vitamin B12 has the same distribution coefficient between ammonium sulfate saturated urine and n-butanol as authentic vitamin B12-Co60. Chromatographic analysis utilizing as a solvent aqueous 2,4-lutidine revealed the radioactive material in the urine to have the same Rf value (.45-.55) as pure vitamin B12. The radioactivity in ileal content and stool under these conditions is not extractable using n-butanol. It is concluded that the Schilling test measures absorption of vitamin B12-C06O from the gut as such and not a degradation product. Hence its use as an assay of intrinsic factor appears justified.