Studies on Easily Split Off Blood Iron by Radioactive Iron Part 2. The Significances of Easily Split Off Blood Iron in the Immature Erythrocyte

Fe(59)-radioactivities in the both hemin iron fraction(Hemin-Fe(59)) and easily split off iron fraction (E S Fe(59)) of the rabbit erythrocyes obtained in reticulocytosis were determined respectively after incubating them with Fe(59) in vitro. On the other hand, immature rabbit erythrocytes labeled with Fe(59) in vivo were incubated in nonradioactive medium, and the same determinations as the above were carried out. The following results were obtained. 1. Reticulocytes of rabbit uptook considerably Fe(59) during incubation in vitro. 2. Fe(59) uptaken in reticulocyte were quickly utilized to the synthesis of hemin. However, Fe(59) at preceding stage of the synthesis were found to be extracted as false ealily split off iron. 3. With the incubation of reticulocytes for 5 hours in vitro, the E S Fe(59) increased after the synthesis of hemin-Fe(59). 4. In vivo, the E S Fe(59) increased in new formed labeled erythrocytes at 6 to 9 hours after intravenous administration of Fe(59), originating from hemoglobin break-down at that stage.