Figure 2. Effects of acetylcholine and epinephrine on AQP5 levels in the apical plasma membrane of parotid tissues from senescent and young adult rats. (A) Parotid slices from 10-week-old (Young) or 115-week-old (Old) rats were incubated for 15 sec at 37°C in the absence (C) or presence (ACh) of 1 µM acetylcholine and 1 µM eserine or incubated for 1 min at 37°C in the absence (C) or presence (Epi) of 10 µM epinephrine. The apical plasma membrane fraction (5 µg of protein) was subjected to immunoblot analysis with anti-AQP5 antibody. (B) Immunoblots were subjected to densitometric analysis, and the amount of AQP5 was expressed as a percentage of the control cell values. Data are expressed as means ± SE of 6 independent experiments. **P < 0.01, ***P < 0.001 vs. the value of the control cells.