The function of PP is to self-regulate pancreatic secretion activities (endocrine and exocrine); it also has effects on hepatic glycogen levels and gastrointestinal secretions.
Its secretion in humans is increased after a protein meal, fasting, exercise, and acute hypoglycemia and is decreased by somatostatin and intravenous glucose.
Plasma PP has been shown to be reduced in conditions associated with increased food intake and elevated in anorexia nervosa. In addition, peripheral administration of PP has been shown to decrease food intake in rodents. PP is secreted by PP pancreatic cells of Langerhans islets. It stimulates the gastric juice secretion, but inhibits the gastric secretion induced by pentagastrine. It is the antagonist of cholecystokinin and inhibits the pancreatic secretion which was stimulated by cholecystokinin. On fasting, PP seric concentration is 80 pg/ml; after the meal, it rises up from 8 to 10 times more; glucose and fats also induce PP's level increase, but on parenteral introduction of those substances, the level of hormones doesn't change. The administration of atropine, the vagotomy, blocks the PP's after-meal secretion. The excitation of the vagus nerve, the administration of gastrin, secretin or cholecystokinin induce PP secretion.