Abstract
In this study, the γ-aminobutyric acid (GABA) transporter at the blood-brain barrier (BBB) was identified by reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and immunostaining analysis, and the transport mechanism was characterized using a conditionally immortalized mouse brain capillary endothelial cell line (TM-BBB) as an in vitro model of the BBB. γ-Aminobutyric acid transport was studied by the cellular uptake of [3H]GABA. [3H]GABA uptake by TM-BBB cells was Na+-, Cl--, and concentration-dependent. The corresponding Michaelis-Menten constant was 679 ± 80 μmol/L and the maximal uptake rate was 4,790 ± 494 pmol/(mg protein · 5 minutes). [3H]GABA uptake by TM-BBB cells was significantly inhibited by betaine, β-alanine, nipecotic acid, taurine, and quinidine, whereas probenecid, L-proline, creatine, and glycine had no effect. This type of inhibition is consistent with the predominant involvement of the GAT2/BGT-1 transporter in TM-BBB cells. RT-PCR analysis showed that GAT2/BGT-1 mRNA was expressed in TM-BBB cells, whereas Western blot analysis showed that TM-BBB cells and mouse brain capillaries express GAT2/BGT-1 protein. Moreover, confocal immunofluorescent microscopy of dual-labeled mouse brain sections demonstrated the colocalization of GAT2/BGT-1 and P-glycoprotein, a BBB-specific marker, on brain capillaries labeled with anti-GAT2/BGT-1 antibody and anti-P-glycoprotein antibody, respectively. These results are evidence that GAT2/BGT-1 is expressed at the BBB and is involved in GABA transport across the BBB.
Original language | English |
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Pages (from-to) | 1232-1239 |
Number of pages | 8 |
Journal | Journal of Cerebral Blood Flow and Metabolism |
Volume | 21 |
Issue number | 10 |
DOIs | |
Publication status | Published - 2001 |
Externally published | Yes |
Keywords
- Blood-brain barrier
- Carrier-mediated transport
- GAT
- GAT2/BGT-1
- Neurotransmitter
- γ-Aminobutyric acid
ASJC Scopus subject areas
- Neurology
- Clinical Neurology
- Cardiology and Cardiovascular Medicine