Gastrin

GI / Digestive

Also known as: Gastrin-17, G-17, Gastrin-34, G-34, Big Gastrin, Little Gastrin, Pentagastrin

GI Regulatory PeptidesResearch phase: Endogenous hormone (well characterized)Regulatory: Endogenous peptide. Pentagastrin (synthetic C-terminal fragment) was used as a diagnostic agent. Serum gastrin is a standard clinical lab test.

Mechanism

Gastrin is the main hormone that tells your stomach to produce acid. Released by G cells in the stomach lining after eating, it stimulates parietal cells to secrete hydrochloric acid and promotes growth of the stomach lining. Elevated gastrin (hypergastrinemia) occurs with acid-blocking medications (PPIs) and gastrinomas (Zollinger-Ellison syndrome). It exists mainly as gastrin-17 and gastrin-34.

Technical detail

Gastrin exists as G-17 (predominant postprandial form, from antral G cells) and G-34 (predominant fasting form, from duodenal G cells), both sharing a C-terminal amidated tetrapeptide (Trp-Met-Asp-Phe-NH2) essential for biological activity. Gastrin binds CCK-B/gastrin receptors (Gq-coupled) on enterochromaffin-like (ECL) cells, stimulating histamine release which then activates H2 receptors on parietal cells for HCl secretion. Direct CCK-BR activation on parietal cells also contributes. Gastrin is trophic for gastric oxyntic mucosa, stimulating ECL cell and parietal cell proliferation via ERK1/2 and JAK-STAT pathways. Somatostatin from D cells provides negative feedback on gastrin release.

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