H2 (Histamine) Receptors

545

Summary

H2 histamine receptors are a type of G-protein coupled receptor that induce gastric acid production in the stomach. When histamine binds to H2 receptors, a Gs-protein subunit is activated, which goes on to cause a downstream signaling cascade. H2 receptors are importantly found on parietal cells in the stomach, where binding induces production and secretion of stomach acid. H2-blocking drugs including cimetidine, famotidine, ranitidine, and nizatidine can be used to reduce gastric acid production, which is useful in the treatment of peptic ulcer disease and acid reflux.

Key Points

  • H2 (Histamine) Receptors
    • GPCR that responds to histamine
      • Activates a Gs subunit
    • Locations
      • Parietal cells of stomach
      • Vascular smooth muscle, heart, immune cells
    • Actions
      • Increase gastric acid secretion
        • Histamine normally produced by enterochromaffin-like cells (ECL) to stimulate parietal cells (oxyntic cells) to produce acid
        • H2 receptor antagonists (e.g. cimetidine, famotidine, ranitidine) used to treat peptic ulcer disease and other acid-mediated disorders