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Gastrin is a peptide hormone coded at 7q12-q21 with two active forms in man:

  1. Gastrin I
    • Seventeen amino acids Glp-Gly-Pro-Trp-Leu-Glu-Glu-Glu-Glu-Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2
  2. Gastrin II
    • sulfate ester group on tyrosine in the 12th position of gastrin I

It is produced by the gastric antral mucosal G cells and to a lesser extent by the D cells of the pancreatic islets. Release is stimulated by gastrin-releasing polypeptide(GRP), a secretagogue from the neurons in the antral mucosa, which also stimulates the release of pancreatic polypeptide, glucagon, gastric inhibitory peptide and insulin.

Its main function is to stimulate H+ ion excretion by the oxyntic gastric mucosa, which in turn inhibits gastrin secretion by mucosal cells of the antrum.

Gastrinomas secrete both gastrin I and gastrin II producing the Zollinger-Ellison syndrome.

A number of synthetic active analogues exist including:

Somatostatin, which is secreted by D cells, including those of the oxyntic mucosa, controls G cell gastrin secretion by modification of its gene transcription.