Observations on Fe59 Labeled Bone Marrow Ferritin

LTHOUGH FERRITIN has been shown to be present in many tissues of the body, the bulk of it is found in the cells of the liver, the spleen, and the bone marrow.”2 Ferritin aggregates with other cellular constituents, it is believed, to form insoluble complexes called hemosiderin.3 Ferritin and hemosiderin constitute the body’s storage depot of iron. Most of this iron supply, derived chiefly from hemoglobin breakdown, is returned to the erythroblasts for reincorporation into heme. Marrow ferritin is found both in reticuloendothelial cells as well as in erythroblasts. Whether the reticuloendothelial cell ferritin of the marrow is an anabolic source of iron for the erythroblast, or whether it is predominantly of catabolic origin, remains obscure to our understanding. Erythroblast ferritin is seen by electron microscopy both in the the cytoplasm and in the cell membrane.4a Marrow ferritin becomes labeled with radioiron during incubation in vitro with this isotope. This is an observation which at first glance seems selfevident, but which was only first documented in 1964 by Zail and associates.6 A polymorphism of labeled bone marrow ferritin is described in the report to follow. This polymorphism appears to be distinct from that previously described in starch gel electrophoresis.79