Figure 3. Time course of the effects of SNI-2011 and acetylcholine on the amount of AQP5 in the apical plasma membrane of parotid tissues from young adult and senescent rats. (A) Parotid slices from 10-week-old (Young) or 115-week-old (Old) rats were incubated at 37°C for 0, 1, 3, 10, or 30 min (lanes 1 to 5, respectively) in the presence of 10 µM SNI-2011. The apical plasma membrane fraction (5 µg of protein) was then subjected to immunoblot analysis with antibodies to AQP5. (B) Immunoblots were subjected to densitometric analysis, and the amount of AQP5 in 10-week-old ( O ) or 115-week-old ( • , solid line) rats was expressed as a percentage of the value for respective control tissues. Parotid slices from 115-week-old ( • , dotted line) rats were incubated at 37°C for 0, 0.25, 1, 3, or 10 min in the presence of 1 µM acetylcholine and 1 µM eserine. Data are means ± SE of values from 3 independent experiments performed with tissues from 3 different rats. *P < 0.05, **P < 0.01, ***P < 0.001 vs. the control value.