Heterogeneous Metabolism of Marrow Ferritins during Erythroid Cell Maturation

S ummary Two metabolically distinct pools of ferritin exist side by side in the bone marrow. One has been designated‘anabolic’ since it accepts iron from transferrin and is presumably an isoferritin characteristic of erythroid cells. The other is primarily‘catabolic’, since it accepts iron from degraded haemoglobin and is considered an isoferritin of reticuloendothelial cells. Both of these isoferritins, however, incorporate iron during the period of erythroid cell maturation in the marrow, although the incorporation proceeds at markedly different rates. The incorporation of iron into both isoferritins can be demonstrated regardless of the route of administration of iron, i.e., whether by transferrin or by degraded haemoglobin. The results support the hypothesis that storage iron moves directly or indirectly from the ferritin pool of the developing erythroid cell to that of the reticuloendothelial cell. They also show that reticulothelial cell ferritin iron undergoes rapid reutilization to re‐enter the iron storage pool of erythroblasts.