Enhancement of Exocrine Pancreatic Function by Trypsin Inhibitor (Leupeptin) Administration in Rats

Abstract

The effect of long-term administration of trypsin inhibitor on the content of exocrine pancreatic enzymes and the in situ secretory responses to a secretagogue in the rat pancreas were examined. Male Sprague-Dawley rats 5 weeks old were used. Each rat received oral administration of leupeptin (50, 200 or 400mg/kg body weight) by orogastric tube once daily for 14 days. Trypsin inhibitor administration did not affect the body weight gain, though it led to a significant dose-dependent increase in pancreatic weight. In the enlarged pancreas, the tissue contents of amylase [EC 3.2.1.1] and trypsin [EC 3.4.21.4] were significantly increased. The changes in the enzyme contents were non-parallel, since the increase in trypsin was more marked than that of amylase. The secretory responses induced by caerulein in leupeptin-administered rats were significantly greater than those in the control rats. The basal flow of pancreatic juice in leupeptin-administered rats before stimulation was more than twice that of the control. However, the basal output levels of amylase and protein in the leupeptinadministered rats were similar to the corresponding values in the control. From these findings, it was concluded that trypsin inhibitor induces not only the secretion of CCK-PZ but also secretin.