Transferrin receptors in rat brain: neuropeptide-like pattern and relationship to iron distribution

The authors have characterized and visualized the binding of 125I-labeled transferrin to sections of rat brain. This saturable, reversible, high-affinity binding site appears indistinguishable from transferrin receptors previously characterized in other tissues. Moreover, a monoclonal antibody raised to rat lymphocyte transferrin receptors could immunoprecipitate recovered intact transferrin solubilized from labeled brain slices. The pattern of transferrin receptor distribution visualized in brain with both 125I-labeled transferrin and an anti-transferrin receptor monoclonal antibody are almost indistinguishable but differ from the pattern of iron distribution. Iron-rich brain areas generally received neuronal projections from areas with abundant transferrin receptors, suggesting that iron may be transported neuronally. However, many brain areas with a high density of transferrin receptors appear unrelated to iron uptake and neuronal transport and form a receptor distribution pattern similar to that of other known neuropeptides. This neuropeptide-like distribution pattern suggests that transferrin may have neuromodulatory, perhaps behavioral, function in brain