Studies on the Formation of Ferritin in Red Cell Precursors*

Abstract

The incorporation of transferrin-bound iron59 into ferritin was studied in cultures of human and rat bone marrow, and also in vivo. Using immunochemical methods it was possible to demonstrate isotopic labeling of ferritin in normal marrow cultures, but not in cultures from iron deficient subjects. The labeled ferritin appeared to be present predominantly in red cell precursors and not in reticuloendothelial elements. Evidence was obtained that iron taken up by the erythrocyte precursors in excess of immediate requirements for heme synthesis was incorporated into the storage compound ferritin. Although it is possible that a proportion of the iron in labeled ferritin was utilised for heme formation, no positive evidence to support this was obtained, and the results of several studies were compatible with the thesis that excess ferritin iron leaves the red cell precursors while these cells are still in the marrow.