Characteristics of intracellular iron transport in erythroid cells

Transferrin mediated uptake of iron is the physiological and most efficient way for introduction of iron into vertebrate cells. Though not accepted by all investigators, receptor-mediated endocytosis of ferric-transferrin is thought to be the normal mechanism of iron uptake. However, the concept of this pathway does not answer many elementary questions about the internalization of iron, its release from transferrin, its transfer to the cytosol, and the possible existence of a transport intermediate. To contribute to the knowledge of intracellular iron metabolism we aimed to obtain answers to the following questions: What is the nature of the low molecular weight iron binding fraction found in reticulocytes? At what point in the transferrin cell cycle does iron leave the endosome; and what are the conditions necessary for endosomal iron release? In chapter 3 the composition of the low molecular weight iron binding fraction is analyzed to determine the existence of physiologically important low molecular weight iron transporting species in the cytosol. Chapter 4 discusses in the phase of the transferrin cycle at which iron is removed from endosomes. In chapter 5 the experimental work is described which explores the presence of endogenous acceptor molecules for iron released from isolated endosomes