Abstract
This study was carried out to investigate the transport mechanism of basic fibroblast growth factors (bFGF) through blood-brain barriers (BBB). Following an internal carotid artery perfusion, 125I-bFGF was transcytosed through the BBB from blood into brain parenchyma. The saturable binding of 125I-bFGF to the isolated bovine brain capillaries (Kd = 40 nM, and Bmax = 200 pmol/mg) was significantly inhibited by unlabelled bFGF, poly-L-lysine, heparin and glycosaminoglycans with a sulfate residue. The heparin-resistant binding of 125I-bFGF to the conditionally immortalized mouse brain capillary endothelial cell lines (TM-BBB) was saturable and showed significant dependence on temperature and medium osmolarity. This binding was effectively inhibited in cells treated with heparinase, sodium chlorate and an antibody specific to perlecan, a HSPG. Finally, RT-PCR analysis revealed expression of perlecan, and FGF receptors (FGFR1 and FGFR2) mRNA in TM-BBB. These results are consistent with the conclusions, 1) 125I-bFGF is transcytosed through the BBB, and 2) transport of 125I-bFGF through the BBB may be, in part, ascribed to endocytosis mechanism that is triggered by binding to HSPG.
