The effect of chronic exercise on the rat pancreas.

Background: We recently demonstrated that chronic physical exercise increases pancreatic protein content and basal amylase secretion. It is unknown whether chronic exercise causes hypertrophy or proliferation of pancreatic acinar cells.

Methods: Female F344 rats (age, 6 wk) were divided into control (n = 7) and exercise (n = 6) groups. Food consumption was matched between the 2 groups. Rats in the control group were kept sedentary. Rats in the exercise group were exercised for 60 min, 5 d/wk during the experiment. After 8 wk, the pancreas and hindlimb muscles were rapidly excised and weighed. Protein and DNA content and enzyme activity in pancreatic tissue were measured. Pancreatic tissues from control and exercised rats were also prepared for transmission electron microscopy.

Results: Inhibition of growth and hypertrophy of hindlimb muscles were exhibited by the exercise group. In the exercise group, pancreatic wet weight, protein content, and amylase and lipase activities, but not DNA content, were significantly higher than those in the control group. Electron micrographs clearly revealed that acinar cells were hypertrophied and zymogen granules were increased in number in exercised rats.

Conclusion: Chronic endurance exercise increases pancreatic weight, protein content and enzyme activity through hypertrophy of acinar cells.