Figure 5. Regulation of the AQP5 gene expression in RPE cells. The mRNA levels were determined with real-time RT–PCR analysis after stimulation of the cells for 2, 6, and 24 h, and are expressed as folds of isoosmotic unstimulated control. A. Effect of hyperosmotic culture medium (+ 100 mM NaCl) on the gene expression level of various AQP subtypes (n=8). B. Effect of hyperosmotic medium (+ 100 mM sucrose) on the gene expression of AQP5 (n=4). C. Dose-dependent effect of high extracellular NaCl on the cellular level of AQP5 mRNA (n=4). The cells were cultured for 6 h in media that were made hyperosmotic by the addition of 10 to 100 mM NaCl. D. Effect of hypoosmotic medium (60% of control osmolarity) on the gene expression of AQP5 (n=6). E. Effects of high (25 mM) glucose (n=7), CoCl₂ (150 µM; n=8), and fetal bovine serum (10%; n=4) on the gene expression of AQP5. F. Regulation of AQP5 expression by triamcinolone acetonide (50 µM) under isoosmotic (control; n=8) and hyperosmotic (+ 100 mM NaCl; n=6) conditions. Data are means ± SEM obtained in independent experiments performed in triplicate. Significant difference versus isoosmotic unstimulated control: *p<0.05.