Figure 5. Purinergic receptor signaling involved in mediating osmotic and hypoxic expression of the OPN gene in RPE cells. The level of OPN mRNA was determined with real-time reverse transcription (RT)–PCR in cells cultured for 24 h in iso- (control; A) and hyperosmotic (+ 100 mM NaCl) media (B), and in the presence of CoCl₂ (150 µM; C), respectively. The following agents were tested: the ATP/ADP phosphohydrolase apyrase (10 U/ml), the P2X₇ receptor antagonist A-438079 (50 nM), the P2Y₁ receptor antagonist MRS2179 (30 µM), the P2Y₂ receptor antagonist AR-C 118925XX (AR-C; 10 µM), the ecto-ATPase inhibitor ARL-67156 (50 µM), the adenosine A₁ receptor antagonist DPCPX (50 nM), the adenosine A_2A receptor antagonist CSC (200 nM), and the antagonist of nucleoside transporters, NBTI (10 µM). The numbers of independent experiments using cell lines from different donors are indicated in or above the bars. Statistically significant difference versus unstimulated control: *p<0.05. Statistically significant difference versus NaCl control: ^●p<0.05. Statistically significant difference versus CoCl₂ control: ^○p<0.05.