Expression of ferritin protein and subunit mRNAs in normal and iron deficient rat brain

In non-neuronal tissue, ferritin subunit mRNAs are regulated by post-transc riptional mechanisms leading to decreased ferritin protein synthesis during iron deficiency. Biochemical studies have demonstrated that the cerebral f erritin concentration declines during iron deficiency, suggesting that expr ession of ferritin subunit mRNAs in the brain may be regulated by mechanism s similar to those of non-neuronal tissue. However, as ferritin expression has been only vaguely studied in brain, this hypothesis remains to be teste d. We investigated the influence of dietary iron deficiency on the cellular distribution of ferritin protein using immunohistochemistry and H- and L-f erritin subunit mRNAs by non-radioactive in situ hybridization. Pregnant ra ts were subjected to an iron depleted diet (6.4 mg/kg) from the day of conc eption. Litters were kept on the same diet until euthanized at the postnata l age of 10 weeks. This treatment reduced brain iron levels from approximat ely 57 to 26 mu g/g. Reducing the iron stores reduced histochemical detecta ble iron and the expression of ferritin immunoreactivity in neurons, oligod endrocyte-like and microglia-like cells. In normal rats, H- and L-ferritin subunit mRNAs were expressed in virtually all neurons and non-neuronal cell s. The cerebral expression of the ferritin subunit mRNAs was not affected b y iron deficiency. The levels of ferritin subunit mRNAs in the brain were a lso unaltered from iron deficiency when examined by Northern blotting. In c onclusion, brain levels of iron and ferritin protein are highly susceptible to dietary iron deficiency, whereas the cerebral expression of H- and L-fe rritin subunit mRNAs remains unchanged. (C) 1999 Elsevier Science B.V. All rights reserved.