Single intracerebral injection of apotransferrin in young rats induces increased myelination.

Three-day-old rats were injected intracranially with 210 or 350 ng of apotransferrin (aTf) to study the possible neurotrophic effects of this iron transport protein. Treated animals and appropriate controls were injected with saline, denatured aTf or ovalbumin. Myelin was isolated from the brains and used to study its chemical composition and the protein electrophoretic pattern. Total myelin galactolipids and especially total phospholipids were significantly increased with reference to controls at both ages studied. A slight increase in total cholesterol was also observed. Total myelin proteins were markedly increased both at 10 and 17 days in comparison to controls. Chloroform:methanol-soluble proteins (proteolipids) were only slightly increased. The electrophoretic profile showed that the two main bands corresponding to myelin basic protein (MBP) were relatively increased in the treated animals. The enzymatic activity of 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) was significantly increased. The changes observed were dose- and age-dependent. The injection of aTf was effective only within a short developmental period since animals treated at 20 days of age showed no apparent changes in myelin composition. The actions of aTf injection persisted at least up to 60 days, since at this age the myelin obtained from injected animals still contained higher amounts of total proteins phospholipids and galactolipids in comparison to control animals. The action of aTf appears to be specific for myelin, since no significant effects were observed in membranes of a total brain homogenate. The effects are specific for the apoprotein injected since other proteins (ovalbumin) or heat-denatured aTf were ineffective.