Gastrin – produced by G cells in stomach antrum
• Secretion stimulated by amino acids, vagal input (acetylcholine), calcium, ETOH, antral distention, pH > 3.0
• Secretion inhibited by pH < 3.0, somatostatin, secretin, CCK
• Target cells – parietal cells and chief cells
• Response – ↑ HCl, intrinsic factor, and pepsinogen secretion
• Omeprazole blocks H/K ATPase of parietal cell (final pathway for H+ release)
Somatostatin – mainly produced by D (somatostatin) cells in stomach antrum
• Secretion stimulated by acid in duodenum
• Target cells – many; is the great inhibitor
• Response – inhibits gastrin and HCl release; inhibits release of insulin, glucagon, secretin, and motilin; ↓ pancreatic and biliary output
• Octreotide (somatostatin analogue) – can be used to ↓ pancreatic fistula output
CCK – produced by I cells of duodenum
• Secretion stimulated by amino acids and fatty acid chains
• Response – gallbladder contraction, relaxation of sphincter of Oddi, ↑ pancreatic enzyme secretion
Secretin – produced by S cells of duodenum
• Secretion stimulated by fat, bile, pH < 4.0
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