Blood-brain barrier transport of 125I-labeled basic fibroblast growth factor.
OBJECTIVE
This study was carried out to examine the blood-brain barrier (BBB) transport of human basic fibroblast growth factor (bFGF) and investigate its mechanism.


METHODS
The BBB transport of 125I-bFGF was measured by several in vivo methods including intravenous administration, in situ internal carotid artery perfusion, and intracerebral microinjection. The in vitro binding of 125I-bFGF was characterized using freshly prepared bovine brain capillaries.


RESULTS
The distribution volume of 125I-bFGF in the postvascular supernatant increased with the perfusion time, and exceeded the space occupied by the brain microvasculature and its trichloroacetic acid (TCA) precipitability was more than 90%. 125I-bFGF avidly bound to isolated bovine brain capillaries with a Bmax of 206 +/- 48 pmol/mg protein, and a Kd of 36.5 +/- 15.7 nM. This binding was significantly inhibited by unlabeled bFGF and heparin in a concentration-dependent manner. The cationic peptides, protamine and poly-L-lysine (each 300 microM), produced over 85% inhibition of 125I-bFGF binding to brain capillaries. Furthermore, glycosaminoglycans with a sulfate residue, chondroitin sulfate B and C (each 10 microg/mL) also inhibited the binding of 125I-bFGF The in vivo transcytosis of 125I-bFGF from the luminal side to the brain was also inhibited by the presence of heparin (10 microg/mL) and poly-L-lysine (300 microM), whereas neither hyaruronic acid (10 microg/mL) nor insulin (10 microM) had any effect. In addition to these results, the brain efflux index method was used to confirm that the transcytosis of 125I-bFGF from brain to blood across the BBB was negligible.


CONCLUSIONS
These results suggest that 125I-bFGF is transported across the BBB, possibly by an adsorptive-mediated transcytosis mechanism that is triggered by binding to negatively charged species on the luminal membrane surface of the brain microvasculature, such as heparan sulfate proteoglycans.
Deguchi
Y
Y
Department of Biopharmacy, School of Pharmaceutical Sciences, University of Shizuoka, Japan. deguchi@ys7.u-shizuoka-ken.ac.jp
Naito
T
T
Yuge
T
T
Furukawa
A
A
Yamada
S
S
Pardridge
W M
WM
Kimura
R
R
D000818:Animals; D001692:Biological Transport; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism; D002196:Capillaries / Q000378:metabolism; D002343:Carotid Artery, Internal / Q000378:metabolism; D002417:Cattle; D016222:Fibroblast Growth Factor 2 / Q000493:pharmacokinetics*; D006801:Humans; D007275:Injections, Intravenous; D007457:Iodine Radioisotopes; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D007457:Iodine Radioisotopes; D016222:Fibroblast Growth Factor 2