Exocrine pancreatic function following proximal small bowel resection in rats.

1. In order to assess if proximal enterectomy induces changes in the function of the exocrine pancreas, the exocrine pancreas was studied 1 week, 4 weeks, and 6 months after 50 or 75% proximal small bowel resection. 2. One week after 50 and 75% proximal small bowel resections, basal pancreatic bicarbonate outputs, studied by means of an external pancreatic fistula in conscious rats, were increased significantly over control values by 43 and 78% respectively. Four weeks after a 75% resection, the bicarbonate output was still significantly higher in resected animals than in sham operated animals. 3. The increase of volume and bicarbonate of the basal pancreatic secretion coincided with a 4-fold increase in plasma secretin concentration 1 week after resection. Both increased pancreatic secretion and plasma secretin concentration were transient. 4. The pancreatic hypersecretion was specifically reversed to control values with an I.P. injection of jejunoileal mucosa homogenate. 5. Serum gastrin and somatostatin values in intestinal mucosa and pancreas were not changed 1 and 4 weeks after enterectomy compared with sham operated animals. 6. The weight of the pancreas and its content of DNA were unaltered by resection. Amylase and chymotrypsinogen per gram pancreatic tissue and per microgram DNA were reduced 4 weeks following resections as compared with sham operated rats. After 6 months, chymotrypsinogen appeared further reduced in resected animals. 7. It is concluded that extensive proximal enterectomy in rats produced early, transient and marked increases in basal pancreatic water and bicarbonate secretion and in plasma secretin due to the loss of jejunoileal inhibitor(s), and a selective decrease in certain enzymes in pancreatic tissue.