Gastrin is secreted by G cells of the gastric antrum and stimulates gastric acid secretion. The predominant mechanism by which gastrin activates parietal cells is through the release of an intermediary substance from which cell type?

• A D cells releasing somatostatin
• B Enterochromaffin cells releasing serotonin
• C Chief cells releasing pepsinogen
• D Enterochromaffin-like (ECL) cells releasing histamine ✓

Explanation

Gastrin binds CCK-D/gastrin receptors on enterochromaffin-like (ECL) cells in the oxyntic mucosa, triggering histamine release. Histamine then acts on H2 receptors on parietal cells to activate the H+/K+-ATPase. This paracrine histamine pathway is the dominant mechanism, though gastrin also has a weak direct effect on parietal cells. Somatostatin from B cells inhibits acid secretion, making option A incorrect.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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