PP is a thirty-six amino-acid peptide produced by PP or F cells that are found mainly in the islets of Langerhans but are also scattered through the exocrine pancreas. It was first isolated as a contaminant during the purification of insulin from the pancreas. It has no obvious physiological function. At pharmacological concentrations, PP is a weak inhibitor of gallbladder contraction, pancreatic secretion, and gastric acid output. It is released into the circulation after meals, and in response to activation of cholinergic nerves from the vagus and to pancreatic exocrine stimulants such as CCK.
