METABOLIC AND MOLECULAR HETEROGENEITY OF MARROW FERRITIN

Two isotopes of iron were utilized to label erythroblast and reticuloendothelial cell ferritin in rabbit marrow in vivo. 59Fe was administered by way of the transferrin pathway and 55Fe as heat-damaged labeled reticulocytes. Following clearance of these isotopes from the circulation, the marrow ferritin was isolated and submitted to analytical procedures. The results indicate that erythroblast ferritin, identified by the 59Fe label, can be distinguished from reticuloendothelial-cell ferritin tagged with 55Fe. In comparison with reticuloendothelial-cell ferritin, erythroblast ferritin has (1) a more electronegative character by electrophoresis and ion-exchange chromatography, (2) larger molecular size by gel filtration and (3) lesser iron content by density-gradient centrifugation. © 1969.