A Tracer Study of Iron Metabolism with Radioactive Iron

The metabolism of iron is one of the most important subjects in the field of mineral metabolism. ,There have been numerous investigations of its problems, but until recently they have been seriously limited by the methods of study available. The production of radioactive isotopes of iron (1, 2) provided a new research tool which has proved of great value in the investigation of this field. Iron labeled with radioactive isotope may be distinguished from the iron originally present in the body, and so the fate of a given dose of radioiron’ may be determined with some precision. Previous work with radioiron in the rat (3) and in dogs (4) and humans (5) was handicapped by the low specific activity of the preparations of the radioactive isotope, Fe5g, which were hitherto available. This necessitated the use of massive doses of iron beyond the normal physiological limits. In the present work, use was made of the radioactive isotope Fe55, which is prepared in the cyclotron by bombardment of manganese with deuterons.2 Since the only contamination with inert iron is that occasioned by traces of iron in the manganese probe, this isotope may be prepared with a very high specific activity. This made possible the use of very small doses (0.05 mg.) approaching tracer levels. These tracer doses were administered to rats by stomach tube or by injection, and studies were made of the absorption, excretion, storage, utilization, and distribution of iron under certain experimental conditions.