ROLE OF PEPTIDE YY IN REGULATION OF DUODENAL MOTILITY DURING THE INTERDIGESTIVE PERIOD IN SHEEP

Temporal coordination between duodenal migrating myoelectric complexes (MMC) and pancreatic exocrine secretion, and the effects of porcine p eptide YY (PYY) on gastroduodenal motility and pancreatic exocrine sec retion were examined during the interdigestive period in conscious mat ure sheep. Fluid and enzyme secretions from the exocrine pancreas show ed a periodic pattern corresponding to the phases of duodenal MMC, alt hough these secretion rates were maintained at a high level during pha se II in sheep. Intravenous continuous infusion of PYY at doses rangin g from 50 to 200 pmol.kg(-1).h(-1) or intravenous bolus infusion of PY Y at doses ranging from 50 to 200 pmol.kg(-1) showed a tendency to pro long the first cycle of the duodenal MMC and significantly shorten the second cycle. However, there was almost no effect on ruminal contract ions from the PYY administration. In the pancreatic exocrine secretion , PYY could inhibit only bicarbonate secretion at only the highest dos e of 200 pmol.kg(-1). These results imply that endogenous PYY may play a physiological role in the regulation of the duodenal MMC cycles in sheep but not in ruminal contractions. PYY seems unlikely to regulate the pancreatic exocrine secretion in normal sheep, because a supraphys iological dose of PYY was required to inhibit the pancreatic exocrine secretion.