Jr. Connor et al., A HISTOCHEMICAL-STUDY OF IRON-POSITIVE CELLS IN THE DEVELOPING RAT-BRAIN, Journal of comparative neurology, 355(1), 1995, pp. 111-123
The establishment of normal iron levels in the neonatal brain is criti
cal for normal neurological development. Studies have shown that both
iron uptake and iron concentration in the brain are relatively high du
ring neonatal development. This histochemical study was undertaken to
determine the pattern of iron development at the cellular level in the
rat forebrain. Iron-stained cells were observed as early as postnatal
day (PND) 3, which was the earliest time point examined. At PND 3, th
ere were four major foci of iron-containing cells: the subventricular
zone and three areas within the subcortical white matter. These latter
foci are associated with myelinogenic regions. The blood vessels were
prominently stained for iron throughout the brain. At PND 7, as in PN
D 3, the majority of the iron-containing cells were in white matter. H
owever, there were also patches of iron staining located specifically
in the layer IV of the somatosensory cortex. These cortical patches we
re no longer visible by PND 14. At PND 14, numerous iron-stained cells
were dispersed throughout white matter regions and the tanycytes alig
ning the third ventricle were prominently stained. The blood vessel st
aining was less prominent than at earlier time periods. By PND 28, the
adult pattern of iron staining was emerging. Iron-stained cells were
aligned in rows in white matter and had an apparent preference for a l
ocation near blood vessels. This clustering of iron-positive cells aro
und blood vessels gave the white matter a ''patchy'' appearance. The p
attern of development, cell distribution, and morphological appearance
of the iron-stained cells are consistent with that reported for oligo
dendrocytes. That iron-positive cells in the neonate may be oligodendr
ocytes is consistent with the reports for iron staining in adult brain
s. The recent reports that oligodendrocytes are highly susceptible to
oxidative damage would be consistent with the high iron levels found i
n these cells. These results indicate that oligodendrocytes play a maj
or role in the development of iron homeostasis in the brain. The role
of iron in oligodendrocytes may be associated with metabolic demands o
f myelinogenesis, including cholesterol and fatty acid synthesis. Howe
ver, these cells may be a morphologically similar but functionally dis
tinct subset of oligodendrocytes whose function is to regulate the ava
ilability of iron in the brain. (C) 1995 Wiley-Liss, Inc.