Pancreatic polypeptide inhibits exocrine pancreatic responses to six stimulants

We determined the effects of three different doses of pancreatic polypeptide (50, 200, and 800 pmol X kg-1 X h-1) on pancreatic responses to graded doses of intravenous secretin, caerulein, and bethanechol and intraduodenal HCl, L-phenylalanine, and sodium oleate in dogs. The two lowest doses of pancreatic polypeptide (PP), which produced blood levels lower than measured after a meal, significantly inhibited the pancreatic responses to secretin, caerulein, HCl, and L-phenylalanine; the highest dose of PP inhibited the responses to bethanechol and sodium oleate. There was no difference in the degree of inhibition of bicarbonate or protein secretion caused by pancreatic polypeptide. With secretin, caerulein, bethanechol, and sodium oleate, inhibition was most pronounced against lower doses and was surmountable with higher doses of these stimulants. Inhibition of responses to HCl and L-phenylalanine was observed at all doses of these stimulants. Inhibition of the exocrine pancreatic secretory responses to six different stimulants by PP suggests that this hormone may play an important role in regulation of postprandial pancreatic secretion.