The density of [125I]-transferrin binding sites on perikarya of melanized neurons of the substantia nigra is decreased in Parkinson's disease.

The density of [125I]-diferric-transferrin binding sites was investigated at the cellular level on melanized neurons located in the mesencephalon of patients with Parkinson's disease and control subjects, using quantitative autoradiography of in vitro incubated brain sections. In parkinsonian patients mean densities were reduced, the difference being statistically significant for the ventral tier of the substantia nigra, which is the subregion most affected by neuronal death in the disease. The absence of increase in the number of transferrin receptors on the perikarya within a population of neurons accumulating iron probably reflects the post-transcriptional gene regulation of the number of transferrin receptors that depends upon iron content in eukaryote cells.