Figure 6. Plasma membrane channel-mediated regulation of NaCl-induced expression of the AQP8 gene in RPE cells. A: The level of AQP8 mRNA was determined with real-time RT–PCR analysis in cells cultured for 6 h in iso- (control) and hyperosmotic (+ 100 mM NaCl) media (as indicated by the panels of the bars), and is expressed as folds of unstimulated control. The following agents were tested: the sulfonylureas glibenclamide (Gliben; 50 and 100 µM) and glipizide (Glipi; 50 and 100 µM), the blocker of organic anion transporters, probenecide (1 mM), the pannexin inhibitor carbenoxolone (5 µM), the pannexin-blocking peptide ¹⁰panx (200 µM), and the scrambled control peptide ¹⁰panxScr (200 µM). Vehicle control was made with dimethyl sulfoxide (DMSO; 1:500). B: Effect of pinacidil (100 µM) on expression of the AQP8 gene under control conditions. The mRNA level was determined in cells cultured for 2, 6, and 24 h (as indicated by the panels of the bars), and is expressed as folds of unstimulated control. Each bar represents mean ± standard error of the mean (SEM) obtained in three to ten independent experiments using cell lines from different donors. Significant difference vs. unstimulated control: *p<0.05. Significant difference vs. NaCl control: ^●p<0.05.