Functional Behaviour of Transferrin

Radioactive iron was preferentially bound in vitro to the two functionally different binding sites of transferrin, referred to as hemoglobin‐orientated and nonhemoglobin‐orientated binding site, respectively. Its availability from these binding sites for different organs was tested in vivo in rats.To distinguish different iron uptake characteristics by different organs from the two binding sites of the injected transferrin, the normally high percentage of the erythropoiesis‐related iron clearance was cut down to a level similar to the degree of radioactive iron clearance to the storing organs liver and spleen by a hypertransfusion‐induced polycythemia.It was observed that the iron from the hemoglobin‐orientated binding site was taken up predominantly by bone marrow and intestine, while liver and spleen had a higher affinity to iron bound to the nonhemoglobin‐orientated binding site, thus indeed pointing out a different function of the two binding sites.