Secretin porcine stimulates pancreatic and gastric secretions to aid in the diagnosis of pancreatic exocrine dysfunction and the diagnosis of gastrinoma. Porcine Secretin for Injection administered intravenously stimulates gastrin release in patients with gastrinoma whereas only small changes in serum gastrin concentrations occur in healthy subjects and patients with peptic ulcer disease. The primary action of secretin is to stimulate pancreatic ductal cells to secrete pancreas fluid in large volumes that contain bicarbonate. Secretin is a hormone that is normally released from the duodenum upon exposure of the proximal intestinal lumen to gastric acid, fatty acids, and amino acids. Secretin is released from enterochromaffin cells in the intestinal mucosa. Secretin receptors have been identified in the pancreas, stomach, liver, colon, brain and other tissues. When secretin binds to secretin receptors on pancreatic duct cells it opens cystic fibrosis transmembrane conductance regulator (CFTR) channels, leading to secretion of bicarbonate-rich pancreatic fluid. Secretin may also work through vagal-vagal neural pathways since stimulation of the efferent vagus nerve stimulates bicarbonate secretion and atropine blocks secretin-stimulated pancreatic secretion.