Hypertonicity enhances GABA uptake by cultured rat retinal capillary endothelial cells

Tohru Yahara, Masanori Tachikawa, Shin Ichi Akanuma, Ken Ichi Hosoya

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)611-615
Number of pages5
JournalDrug metabolism and pharmacokinetics
Volume25
Issue number6
DOIs
Publication statusPublished - 2010

Keywords

  • Hypertonicity
  • Retinal capillary endothelial cells
  • Taurine transporter (TauT)
  • γ-Aminobutyric acid (GABA)

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science
  • Pharmacology (medical)

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