In vitro Assay of Hog Intrinsic Factor Concentrates Employing Paper Electrophoresis and Co 60 -B 12 . ∗

Summary

Simultaneous use of paper electrophoresis and radioactive Vit. B₁₂ permits separation and quantitation of the various B₁₂ binding components present in commercial intrinsic factor concentrates of hog origin. The amount of one particular binder has been found to correlate with the clinical activity of the concentrates as measured by the urinary excretion method of Schilling. This provides the basis for a simple in vitro assay of potency of hog intrinsic factor concentrates ranging in level of activity from 2.0 mg to 75.0 mg. It is predicted that pure hog intrinsic factor will be active clinically at a level of 0.1 mg; calculations suggest that it will bind 23 μg B₁₂/mg and have a molecular weight of 60,000.