Kinetics of iron absorption in normal dogs

¹ Department of Pathology, College of Physicians and Surgeons, Columbia University, New York City; and Department of Pathology, College of Medicine, University of Kentucky, Lexington, Kentucky

By means of the simultaneous use of two radioactive isotopes of iron, it has been possible to measure the rate of iron absorption from the gastrointestinal tract in normal dogs. One isotope was administered orally and another intravenously. By suitable calculation the rates of absorption at any given time were computed. Absorption begins at a very high rate, which varied from 22.8 µg/hr to 578 µg/hr in different dogs. The half-time of the absorption rate varied from 0.25 to 0.66 hr. The rapid fall in the rate of iron absorption is not caused entirely by the passage of the labeled material along the intestinal tract, but seems rather to be caused by the development of an inhibitory mechanism or the presence of a rate-limiting reaction in one of the steps in the passage of iron from the intestinal lumen to the plasma.