OBSERVATIONS ON SUBCUTANEOUS MACROPHAGES. PHAGOCYTOSIS OF IRON‐DEXTRAN AND FERRITIN SYNTHESIS

Abstract

The structure of macrophages at the site of subcutaneous injections of iron‐dextran has been studied with the electron microscope. Iron‐dextran has a macromolecular structure which can be distinguished from that of its metabolic product, the iron‐storage protein ferritin. By a process of pinocytosis the macrophages ingest iron‐dextran, then concentrate it within cytoplasmic vacuoles, apoferritin is synthesized and the iron is finally stored within this protein to form ferritin. At first individual molecules of ferritin are uniformly distributed throughout the cytoplasm, accompanied by a few molecules in the nucleoplasm but, as a rule, none in mitochondria. One week after injection, vacuoles containing a mixture of iron‐dextran and ferritin are found, and these are gradually replaced by vacuoles containing only ferritin. © 1961 The Physiological Society