TY - JOUR
T1 - Hypertonicity enhances GABA uptake by cultured rat retinal capillary endothelial cells
AU - Yahara, Tohru
AU - Tachikawa, Masanori
AU - Akanuma, Shin Ichi
AU - Hosoya, Ken Ichi
N1 - Funding Information:
Acknowledgments: This study was supported, in part, by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS).
PY - 2010
Y1 - 2010
N2 - We have reported previously that taurine transporter (TauT) mediates g-aminobutyric acid (GABA) as a substrate in a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells). This study investigates how TauT-mediated GABA transport is regulated in TR-iBRB2 cells under hypertonic conditions. [3H]GABA uptake by TR-iBRB2 cells exposed to 12 h- to 24 h-hypertonic culture medium was significantly greater than that of isotonic culture medium. [3H]GABA uptake by TR-iBRB2 cells was N+H-, Cl-H-, and concentration-dependent with a Michaelis-Menten (Km) constant of 3.5 mM under isotonic conditions and Km of 0.324 and 5.48 mM under hypertonic conditions. Under hypertonic conditions, [3H]GABA uptake by TR-iBRB2 cells was more potently inhibited by substrates of TauT, such as taurine and b-alanine, than those of GABA transporters such as GABA, nipecotic acid, and betaine. These results suggest that an unknown high-affinity GABA transport process and TauT-mediated GABA transport are enhanced under hypertonic conditions. In conclusion, hypertonicity enhances GABA uptake by cultured rat retinal capillary endothelial cells.
AB - We have reported previously that taurine transporter (TauT) mediates g-aminobutyric acid (GABA) as a substrate in a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells). This study investigates how TauT-mediated GABA transport is regulated in TR-iBRB2 cells under hypertonic conditions. [3H]GABA uptake by TR-iBRB2 cells exposed to 12 h- to 24 h-hypertonic culture medium was significantly greater than that of isotonic culture medium. [3H]GABA uptake by TR-iBRB2 cells was N+H-, Cl-H-, and concentration-dependent with a Michaelis-Menten (Km) constant of 3.5 mM under isotonic conditions and Km of 0.324 and 5.48 mM under hypertonic conditions. Under hypertonic conditions, [3H]GABA uptake by TR-iBRB2 cells was more potently inhibited by substrates of TauT, such as taurine and b-alanine, than those of GABA transporters such as GABA, nipecotic acid, and betaine. These results suggest that an unknown high-affinity GABA transport process and TauT-mediated GABA transport are enhanced under hypertonic conditions. In conclusion, hypertonicity enhances GABA uptake by cultured rat retinal capillary endothelial cells.
KW - Hypertonicity
KW - Retinal capillary endothelial cells
KW - Taurine transporter (TauT)
KW - γ-Aminobutyric acid (GABA)
UR - http://www.scopus.com/inward/record.url?scp=78951492741&partnerID=8YFLogxK
U2 - 10.2133/dmpk.DMPK-10-NT-057
DO - 10.2133/dmpk.DMPK-10-NT-057
M3 - 学術論文
C2 - 20930424
AN - SCOPUS:78951492741
SN - 1347-4367
VL - 25
SP - 611
EP - 615
JO - Drug Metabolism and Pharmacokinetics
JF - Drug Metabolism and Pharmacokinetics
IS - 6
ER -