Transcytosis of 6.6-nm gold-labeled transferrin: an ultrastructural study in cultured porcine blood-brain barrier endothelial cells

The mechanism and regulation of iron transport to the brain are largely unknown. The large surface area of the blood–brain barrier capillaries and the presence of transferrin receptors on the luminal plasma membranes of the blood–brain barrier endothelial cells (BBB-ECs) suggest that these cells actively participate in the transport of iron into the brain. In this paper, we describe the ultrastructural morphology of primary and first-passage cultures of BBB-ECs grown on different types of porous membranes. To investigate the mechanism of iron transport into and across the BBB-ECs, porous membrane grown first-passage cells were incubated with 6.6-nm gold-labeled transferrin and studied with electron microscopy. Results are suggestive for a transcytosis of transferrin through the BBB-ECs.