Transport of [125I]transferrin through the rat blood-brain barrier.
Transferrin receptors are present in the plasma membrane of brain endothelial cells but it is unclear if these receptors mediate transport of transferrin across the blood-brain barrier (BBB). In the present study, the transport of rat holo-transferrin (rTf) across the BBB in vivo was evaluated in ketamine anesthetized rats (250-300 g) both by in situ brain perfusion coupled with capillary depletion analysis and by thaw-mount autoradiography. [125I]rTf was infused through the right internal carotid artery at a rate of 3.65 ml/min for 2.5-5 min. After a 5 min perfusion, the volume of distribution (VD) of [125I]rTf in the brain homogenate, the postvascular supernatant, or the vascular pellet was 55.8 +/- 4.5, 43.5 +/- 4.8, and 8.7 +/- 2.3 microliters/g, respectively. Co-infusion of [125I]rTf with unlabeled rTf or with a high dose of OX26 monoclonal antibody to the rat transferrin receptor significantly reduced the [125I]rTf transport, and in the presence of 10% rat serum [125I]rTf transport was nearly entirely abolished. The transport of [125I]rTf across the BBB in vivo was demonstrated by thaw-mount autoradiography, which showed silver grains well within brain parenchyma following a 5 min internal carotid artery perfusion. These studies are consistent with the following conclusions: (a) in the absence of competing plasma transferrin, [125I]holo-transferrin is transported through the BBB at a rate comparable to the OX26 monoclonal antibody; and (b) the ability to detect measurable transport of perfused [125I]transferrin is greatly inhibited by a small contamination of the perfusate by rat serum, which contains high concentrations of competing transferrin.
Skarlatos
S
S
Department of Medicine, UCLA School of Medicine 90024, USA.
Yoshikawa
T
T
Pardridge
W M
WM
D000818:Animals; D000911:Antibodies, Monoclonal; D001345:Autoradiography; D001692:Biological Transport / Q000276:immunology / Q000502:physiology; D001798:Blood Proteins / Q000494:pharmacology; D001812:Blood-Brain Barrier / Q000276:immunology / Q000502:physiology*; D002196:Capillaries / Q000378:metabolism; D002339:Carotid Arteries / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow; D014168:Transferrin / Q000493:pharmacokinetics*; D014316:Tritium
D000911:Antibodies, Monoclonal; D001798:Blood Proteins; D007457:Iodine Radioisotopes; D014168:Transferrin; D014316:Tritium