Erythroblast ferritin: synthesis, structure, and function in developing erythroid cells.

Abstract

Abstract The biochemical properties of the isoferritin in erythroid cells designated "erythroblast ferritin" (EF) were investigated in marrow and spleen cells of phenylhydrazine anemic rabbits. Synthesis of the erythroblast apoferritin moiety, demonstrated by in vitro incorporation of 3 H-leucine, is accomplished at an early stage of erythroid maturation but is absent in the reticulocyte, despite continuation of an active incorporation of 59 Fe. The iron of bone marrow EF is in a rapid state of turnover, with T/2 of 3.7 hours as determined by in vitro "chase" studies. Two isoferritins with metabolically distinct iron pools were demonstrated in spleen cells, one identical to EF and the other the isoferritin of reticuloendothelial cells. Marrow EF had an iron:protein ratio of 0.116, compared to 0.234 and 0.272 for liver and spleen ferritin, respectively. The relatively lower iron content of EF may be a reflection of its rapid rate of iron turnover. Iron release from EF was studied, using 59 Fe-labeled EF and dialysis techniques. Lower pH values, chelating agents, (EDTA, NTA, and trisodium citrate), and reducing agents (ascorbic acid, cysteine, and glutathione) all promoted release. The biochemical control of iron release from EF thus resembles that of reticuloendothelial cell ferritin.