Oligodendroglial cell differentiation in rat brain is accelerated by the intracranial injection of apotransferrin

In the present paper we first studied the brain distribution and the time a nd dose dependent effects of apotransferrin, after its intracranial injecti on into young rats and at different post-natal ages. Its action upon the tr ansferrin receptor (TfR) and upon the expression of brain transferrin, as w ell as its effect on the proliferation and differentiation of oligodendrogl ial cells (OLGc) was one of the main objectives of our investigation. Total DNA and BrdU labeling, as an index of cellularity and proliferation, respe ctively, were the same in the control and experimental groups of rats. A si gnificant increase in the MBP+ and CA II+ OLGc, and a decrease in the more immature (A(2)B(5)(+)) OLGc were found in the aTf injected rats. At 10 and 17 days of age, Tf-mRNA decreased to around 20% of the amount present in co ntrol animals. The TfR-mRNA in the animals receiving a single dose of aTf a t 3 days of age showed an ina ease in its expression at 10 and 17 days of a ge, coincident with a higher immunoreactivity of the TW itself of neurons, choroid plexus and brain capillaries in different brain areas. Although TfR + OLGc were present up to 7 days of age in controls and in the Tf injected rats, no positive cells were observed at 17 days of age, even in the aTf in jected rats. Our results give support to the hypothesis that aTf is an impo rtant factor necessary for the maturation of the OLGc, and that the effects that it produces in the OLGc-myelin unit after its intracranial injection in young rats are not due to an increase in proliferation, but to an accele rated differentiation of Tf-sensitive OLGc.