Figure 2.
AQP1 is associated with ZGs in pancreatic acinar cells. (A–D) AQP1 immunofluorescent confocal microscopy on stimulated and resting pancreatic lobules. Pancreatic lobules incubated for 1 h at 37°C in the absence (resting) or presence (stimulated) of the secretagogue, carbamylcholine (1 × 10−5 M). A 4-fold increase in amylase secretion from stimulated pancreatic lobules over resting was observed (data not shown). After incubation, the lobules were fixed, cryosectioned, and processed for immunofluorescent confocal microscopy. Confocal images of AQP1-immunostained pancreatic tissue in resting (A and C) and stimulated (B and D) states indicate association of AQP1 with ZG and its possible involvement in secretion. In resting acinar cells, AQP1 appears distributed throughout the cell including the apical region (arrow). The nuclei (n) located at the basolateral end of pancreatic acinar cells are devoid of AQP1-specific immunostaining. After stimulation of secretion, much of the AQP1 immunoreactivity is localized at the apical region of pancreatic acinar cells, where secretion is known to occur. (Bar = 10 μm.) (E) Immunogold electron microscopic (10-nm particles) localization of AQP1 to ZG (arrowheads). Note some AQP1 associated with the cell plasma membrane (arrow). (Magnification: ×57,000.)