Autoradiography of transferrin receptors in the human brain.

Transferrin is the major protein concerned with iron transport in the serum and may provide a route by which iron enters the brain. This study was designed to show the optimal binding conditions for in vitro transferrin receptor autoradiography and to show the regional distribution of transferrin receptors in the human brain. Optimal binding conditions were: 120 min incubation with 5.0 nM 125I-transferrin at 37 degrees C. Transferrin receptors degrade quickly even with storage at -70 degrees C, therefore binding studies should be performed within 7 days post mortem. Transferrin receptors were widely distributed in the human brain, with high density in the neocortex, moderate densities in the putamen and caudate nuclei, and very low densities in the globus pallidus and substantia nigra. Therefore transferrin receptor density shows a mismatch with the known distribution of iron in the human brain. The presence and distribution of transferrin receptors in the human brain are important because they may provide a route to deliver lipophobic substances across the blood-brain barrier by binding them to antibodies raised against transferrin receptors.