Age-associated changes in pancreatic exocrine secretion of the isolated perfused rat pancreas

Gut functions, such as gastrointestinal motility, gastric secretion and pancreatic secretion, were reduced with age. Glucose tolerance is impaired, and the release of insulin and β-cell's sensitivity on glucose are reduced with age. However, a lot of controversial data have been reported as insulin concentrations after glucose ingestion are either higher or no different in elderly and young subjects. Thus, this study was aimed to investigate whether aging could affect pancreatic exocrine secretion and its action mechanisms. An isolated perfused rat pancreatic model was used to exclude the effects of external nerves or hormones. Pancreatic secretion was increased by CCK under 5.6 mM glucose background in the isolated perfused pancreas of young (3 months), 12 months and 18 months aged rats. There was no significant difference between young and aged rats. In 3 months old rats, CCK-stimulated pancreatic secretion was potentiated under 18 mM glucose background. However, the potentiation effects of endogenous insulin and CCK were not observed in 12 and 18 months old rats. Exogenous insulin also potentiated CCK-stimulated pancreatic secretion in 3 months old rats. Similarly, exogenous insulin failed to potentiate CCK-stimulated pancreatic secretion as that of 3 months old rats. Wet weight of pancreas and amylase content in pancreatic tissue were not changed with age. These results indicate that pancreatic exocrine secretion is reduced with age and endogenous insulin secretion and/or action is involved in this phenomenon.