Diet composition and the plasma levels of some peptides regulating pancreatic secretion in the pig.

The aim of the present work was to study the effect of a modification of diet composition upon the plasma levels of some peptides known to be involved in the hormonal regulation of exocrine pancreas secretion. Six growing Large-White pigs weighing 41 +/- 3.2 kg were fitted with a catheter in a carotid artery; four of these pigs were also fitted with permanent fistulae in the pancreatic duct and duodenum. All the pigs were adapted to a control diet (C) during an 8-day period before surgery. In the 8-day postoperative period and a first experimental period of 4 days, they were fed on the same control diet. Three pigs were then fed the experimental diets in the following sequence: fat-rich diet (F) for 7 days, control diet (C) for 7 days, starch-rich diet (S) for 7 days, whereas the other three pigs were fed the same diets over the same time lengths but in inverse sequence: diet S, diet C, diet F. The three diets were isoproteinic (16% protein) and isocaloric (3,850 cal/kg). The pancreatic secretion and the plasma levels of cholecystokinin (CCK), secretin, pancreatic polypeptide (PP) and somatostatin were analysed during the 4 days of the first experimental period and the last day of each of the other three experimental periods. Total proteins and lipase and amylase activities were determined in pancreatic juice samples collected over the 7 hours following the morning meal. Arterial blood was sampled at 9 h 00 (before meal consumption), 9 h 30, 10 h 00 and every hour until 16 h 00. The results confirm pancreatic adaptation to the diet, i.e. increase of lipase specific activity (x 1.8) when the pigs ingested 6 times more fat (diet S----diet F) per day, and an increase in amylase specific activity (x 2.3) when they ingested 3 times more starch (diet F----diet S) per day. Furthermore, changes in diet composition did not lead to any durable, significant change in plasma peptide levels. In conclusion, CCK, secretin, PP and somatostatin, known to regulate exocrine pancreas secretion, would not be involved in the mechanisms of pancreatic amylase and lipase adaptation to the amount of carbohydrate and fat ingested by pigs.