Fig. 5. Growth factors increase the expression level of GLAST. (A) Western blot analysis of the glutamate transporter GLAST (a) or GLT-1 (b) was performed for the rat whole brain or the cortical astrocytes cultured with either 3 ng/ml bFGF, 100 ng/ml IGF-1 or 30 ng/ml EGF for 36 hours. Anti-GLAST or GLT-1 antibody recognized a protein with a molecular weight of 60 kDa. GLAST expression was increased by the incubation in the presence of bFGF, IGF-1 or EGF. GLT-1 expression was virtually undetected in the astrocyte cultures. (B) Immunohistochemical localization of GLAST (green) in the astrocytes cultured in the absence (a) or presence (b) of 3 ng/ml bFGF for 36 hours (left panels). Propidium iodide (red) was used for the counterstaining. Right panels show a nonspecific staining of the secondary IgG-FITC in the absence of anti-GLAST antibody. The result confirmed that bFGF enhanced the GLAST protein levels. (C) Northern blots were performed by using mRNA isolated from the rat whole brain, or untreated (Control) and 3 ng/ml bFGF-treated astrocytes. Treatment with bFGF for 24 hours induced an increase of GLAST mRNA levels.