The Heterogeneous Distribution of Brain Transferrin

Abstract

Immunocytochemistry with antisera to transferrin has often been used to identify oligodendroglia in tissue sections and cultures, but reaction product also occurs in blood vessel walls and nerve cells. There is considerable species variation. Serum transferrin is largely biosynthesized in the liver, and its established physiological role is the transport of iron to tissue sites and delivery of the metal to the interior of cells that have transferrin receptors on their surfaces. In sections of the central nervous system, the visualization of iron and transferrin generally does not coincide, and transferrin may have importance to normal brain function beyond iron transport. For a comparative analysis of transferrin in rabbit and rat brain, polyclonal antisera were raised against purified serum transferrins of these species. The antisera were used for transferrin immunocytochemistry on vibratome sections and for immunochemical detection on electroblots. Transferrin immunocytochemistry and iron histochemistry were compared. The electrophoretic separation of brain extracts and transfer to nitrocellulose membranes permitted the quantitation of the protein and the study of the carbohydrate chains of tissue-bound transferrins by biotinylated lectins. An unexpected result in the rabbit was the dense immunocytochemical reaction product in Bergmann glia and Golgi epithelial cells. Reaction in the cytoplasm of oligodendrocytes was relatively faint in this species except for some selected white matter tracts, e.g. the inferior cerebellar peduncles. In sections of rat brain, oligodendrocytes and vessel walls reacted vigorously in all locations. Transferrin levels in rat brain were substantially higher than in rabbit brain. In the rabbit, maximum transferrin levels occurred in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)