Neurotrophic effects of transferrin on embryonic chick brain and neural retinal cell cultures.

The viability and differentiation promoting effects of various transferrins [iron-saturated (holo) and iron-depleted (apo) human and chick ovo (conalbumin)-transferrins, and bovine apo-transferrin] were studied, using serum-free, flat-sedimented cell cultures of embryonic chick brain and neural retina. The effects of transferrin (Tf) on the cell cultures depended on the type of Tf used and the parameter measured. Significant differences between brain and neural retina cultures in the effects of apo-ovoTf and iron [supplemented as ammonium-iron (III) citrate] were detected. Maximal levels of mitochondrial activity were observed in the presence of 2 mg/l apo-ovoTf in neural retina cell cultures. In brain cell cultures, 40 mg ovoTf/l were needed to achieve maximal levels. In brain, but not in neural, retina cell cultures ovoTf and optimal concentrations of Fe3+ exhibited similar effects on biochemical parameters of cell function and differentiation. Although, in the absence of ovoTf, neuronal outgrowth on areas not covered by glial cells was inhibited in both cell cultures, the differences were more prominent in neural retina cell cultures. Our data strongly suggest that Tf plays a key role in processes not connected directly with its iron transport capability.