FERRITIN, TRANSFERRIN, AND IRON IN SELECTED REGIONS OF THE ADULT AND AGED RAT-BRAIN

Iron is necessary for normal neural function but it must be stringentl y regulated to avoid iron-induced oxidative injury. The regulation of systemic iron is through the proteins transferrin (iron mobilization) and ferritin (iron sequestration). This study examines the cellular an d regional distribution of iron and the iron-related proteins ferritin and transferrin in selected regions of the adult and aged rat brain. This information is a necessary prerequisite to understanding the mech anism by which iron homeostasis is maintained in the brain. The predom inant cell type containing ferritin, transferrin, and iron throughout the brain at all ages is the oligodendrocyte. Neurons in most brain re gions contain granular iron deposits which become more apparent with a ge. Ferritin and iron are also present in microglial cells in all brai n regions, but are particularly abundant in the hippocampus. These lat ter cells visibly increase in number in all brain regions as the anima l approaches senescence. Another area in which immunostaining is notab le is surrounding the III ventricle, where transferrin is found in the choroid plexus and ependyma and ferritin and iron are present in tany cytes. The results of this study indicate an important role for neurog lia in the regulation of iron in the brain and also implies that a tra nsport system may exist for the transfer of iron between the brain and cerebrospinal fluid. In the normal rodent brain, the principal cell o f iron regulation is the oligodendrocyte; however, the role of microgl ial cells in the sequestration and detoxification of iron may be signi ficant, particularly as the animal ages. With age there is an increase in stainable iron in neurons without a concomitant increase in neuron al ferritin immunostaining, suggesting a ferritin independent accumula tion of neuronal iron with age. (C) Wiley-Liss, Inc.