Developmental and methodological aspects of intestinal and pancreatic function in pigs and rats

Abstract: The gastrointestinal tract has two opposing functions; to effectively absorb nutrients and to act as a safety barrier against hazardous substances in the environment. After birth these functions develops gradually. The present thesis focuses on how the intestinal permeability and pancreatic secretion changes during ontogenic development of the pig, with some methodological aspects on manipulations in animal models in vivo, in situ and in vitro. Since studies have revealed that anesthesia could change the gastrointestinal functions, the pancreatic secretion was measured in pigs under the influence of anesthetic and sedative pharmaceuticals (paper I). It was concluded that general anesthesia or sedation severely depressed or abolished pancreatic exocrine secretion in the young pig. Using adult rats, the relationships between pancreatic stimulation, enzyme secretion and enzymes remaining in the pancreas were elucidated (paper II). The results showed that stimulation of the pancreatic secretion by feeding or by infusion of the secretagogues, CCK and secretin, temporarily drained the pancreas of digestive enzymes, indicating that care must be taken when pancreatic tissue is used for investigating pancreatic function. The effect of the diversion of pancreatic juice was investigated on chronically catheterized pigs (paper III). An increase in the intestinal absorption of protease-sensitive marker molecules was observed. No obvious effect on the pancreatic secretion was found, indicating that feedback inhibition was low during preprandial conditions in pigs. A study on piglets discovered that the profound decrease in macromolecule uptake and passage, at intestinal closure during the first days of life, was reflected by a decreased in vitro permeability in the proximal region of the small intestine (paper IV). During the next two weeks the permeability decreased in the distal region followed by a further decrease and thereby improved barrier properties in the proximal region up to weaning. Weaning is a period of problems for pigs, since their gut is immature. In an attempt to induce maturation by gut exposure to crude red kidney bean lectin before weaning, many parameters in the gut and pancreas indicated precocious maturation after exposure to the crude lectin (paper V). In conclusion, the present thesis delineated the development of many of the gut functions and the possibility to enhance them, but care must be taken in interpretation due to possible intervention by the experimental conditions.