Dynamics of Aquaporin 1 and Aquaporin 8 in the Pancreas : An Experimental Study with a Caerulein-induced Pancreatitis Model

Aquaporins (AQPs) are a family of water channel proteins comprising 13 members, of which five (AQP 1, AQP 4, AQP 5, AQP 8 and AQP12) have been detected in the rat exocrine pancreas. However, the dynamics and role of AQPs in pancreatitis, which is characterized by interstitial edema and acinar cell injury, are unclear. This experimental study using a caerulein-induced pancreatitis model aimed to investigate the kinetics of AQPs in pancreatitis. Male Wistar rats received a caerulein infusion (10 μg/kg/h) for three h and then were sacrificed at three h and 72 h after the start of infusion. The expression of mRNA and protein for AQP1 and AQP8 were examined by quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry. In the control group, AQP1 was located in the pancreatic ductal cells and capillary endothelia, whereas AQP8 was positive only in the acinar cells. Macroscopically and microscopically, obvious pancreatitis was observed in the acute pancreatitis phase (three h group), while it disappeared in the recovery phase (72 h group). AQP1 expression in the pancreatic ductules decreased in both the three h and 72 h groups. AQP8 expression was depressed in the three h group when the acinar cell swelling was observed, while AQP8 expression was focally decreased in the 72 h group. These results suggest that the decrease in AQP1 and AQP8 show a latent injury in the ductal cells and acinar cells. They can be related to the mechanisms of edematous pancreatitis.