title: Increased glutamate uptake and GLAST expression by cyclic AMP in retinal glial cells.
abstract: BACKGROUND
  The aim was to investigate the effect of cyclic adenosine monophosphate (cAMP) on glutamate uptake and glial glutamate aspartate transporter (GLAST) expression in cultured rat retinal glial cells.
  
  
  METHODS
  Retinal glial cell cultures were prepared from 1- to 3-day-old Sprague-Dawley rats. Cultures were treated with dibutyryl-cAMP (dBcAMP) for 24 h. Glutamate uptake was measured as 3H-glutamate content of the lysates as determined by scintillation counting. The expression of GLAST in dBcAMP-treated cells was examined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting.
  
  
  RESULTS
  Cells were identified by immunocytochemistry using antibodies against vimentin and carbonic anhydrase C. Treatment of cultured cells with dBcAMP significantly increased glutamate uptake after 60 min compared with untreated cells (p < 0.01). Maintenance of cells in medium supplemented with dBcAMP increased GLAST mRNA and protein levels. GLAST mRNA levels were elevated 2.9-fold 24 h after treatment. GLAST protein levels were elevated 2.5-fold 24 h after treatment.
  
  
  CONCLUSIONS
  These results indicate that treatment with cAMP increases glutamate uptake through upregulated GLAST activity in cultured retinal glial cells. These findings suggest that retinal glial cells may regulate extracellular glutamate concentration and protect retinal neurons against glutamate excitotoxicity.
authors.affiliation: Department of Ophthalmology, Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo, 105-8461, Japan. tstmski@jikei.ac.jp
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sakai
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshitoshi
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nagai
authors.forename: Kenji
authors.initials: K
authors.lastname: Kitahara
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D003994:Bucladesine / Q000494:pharmacology; D024402:Carbonic Anhydrase II / Q000378:metabolism; D002478:Cells, Cultured; D003470:Culture Media; D000242:Cyclic AMP / Q000494:pharmacology*; D018698:Glutamic Acid / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D009457:Neuroglia / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014746:Vimentin / Q000378:metabolism
chemical_list: D027322:Amino Acid Transport System X-AG; D003470:Culture Media; D012333:RNA, Messenger; D014746:Vimentin; D018698:Glutamic Acid; D003994:Bucladesine; D000242:Cyclic AMP; D024402:Carbonic Anhydrase II