P glycoprotein regulated transport of glutamate at blood brain barrier.
OBJECTIVE
To study whether efflux of glutamate (Glu) at blood brain barrier (BBB) was regulated by P-glycoprotein (P-gp).


METHODS
1) After intracerebral microinjection [3H]Glu 5 min, recoveries were determined in injected cerebrums in presence of multidrug-resistant(MDR) reversing agents verapamil (Ver), vincristine(VCR), an d cyclosporin A(CsA); 2) apparent transfer constants (Kin) of [3H]Glu from plasma to brain were determined after the in situ rat brain perfusion 2 min us ing solution containing MDR-reversing agents; 3) uptake amount of [3H]Glu by prima ry cultured bovine brain capillary endothelial cells(BCEC) was analyzed; and 4) In presence of MDR-reversing agents and antibody of P-gp, C(219), uptake amount of [3H]Glu by luminal membrane vesicles derived from BCEC was also determined.


RESULTS
In control rats, remaining percentage of [3H]Glu in inject ed cerebrums was 25 %+/-16 % at 5 min after intracerebral injection. After pre-treating with CsA 10, 100 micromol/L, VCR 20 micromol/L and Ver 100 micromol/L, the remaining percentages of [3H]Glu were increased to about 2.2, 2.5, 2.3, a nd 2.7 folds of control, respectively. In the in situ rat brain per fusion experiment, VCR and CsA in perfusion medium concentration-dependently increased [3H]Glu BBB permeability to brain. Co-administration o f CsA 40 micromol/L mad e BBB permeability of [3H]Glu in cerebral cortex, hippocampus and striatum increase to about 9, 3, 7, and 4.6 folds of control, respectively. Steady-state uptake of [3H]Glu by BCEC was also increased up to 2.5 folds in presence of 100 micromol/L CsA. MDR-reversing agents and antibody of P-gp, C219, level-dependently inhibited the uptake of [3H]Glu by luminal membrane vesicles of BCEC. And this process is ATP-dependent.


CONCLUSIONS
Efflux of Glu at BBB may be regulated by P-gp.
Liu
X D
XD
Center of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China. xdliu@jlonline.com
Liu
G Q
GQ
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000494:pharmacology*; D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000098:blood supply / Q000166:cytology; D002417:Cattle; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D004730:Endothelium, Vascular / Q000166:cytology; D018698:Glutamic Acid / Q000493:pharmacokinetics*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology; D014750:Vincristine / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018698:Glutamic Acid; D014750:Vincristine; D016572:Cyclosporine; D014700:Verapamil