Ethylenediamine Tetraacetate and the Intestinal Absorption of Vitamin B₁₂

Abstract

FOR the laboratory, as opposed to the clinical, analysis of the defective absorption of vitamin B₁₂ in pernicious anæmia caused by the lack of Castle's intrinsic factor, several methods have been developed since radioactive preparations of the vitamin became available. In the first the absorption is studied by measuring the radioactivity of the fæces produced by gastrectomized rats given a test dose of labelled vitamin B₁₂, with or without an intrinsic preparation^1–3. The defect of absorption in these animals closely resembles that found in pernicious anæmia in humans⁴. In a second method slices or homogenates of rat liver or strips of rat intestine are exposed to a preparation of hog intrinsic factor and simultaneously or afterwards to labelled vitamin B₁₂ ^5–7. With this technically simpler in vitro method hog intrinsic factor was found to increase the uptake of vitamin B₁₂ by the tissue preparation. This effect is dependent on the presence of calcium in the incubation fluid and can be abolished by the addition of ethylene-diamine tetraacetate (as the disodium salt dehydrate) to the medium^8,9.