H2 receptor antagonists like ranitidine inhibit gastric acid secretion. Which cell in the gastric mucosa is the direct target of H2 blockers?

• A G cells (gastrin-secreting cells) in the antrum
• B Enterochromaffin-like (ECL) cells
• C Chief cells (pepsin-secreting cells) in the gastric body
• D Parietal cells (oxyntic cells), which express H2 receptors coupled to adenylyl cyclase increasing cAMP ✓

Explanation

H2 receptors on gastric parietal cells are Gs-coupled, activating adenylyl cyclase and raising intracellular cAMP, which activates protein kinase A and ultimately stimulates the H+/K+-ATPase proton pump. H2 blockers competitively block this receptor, reducing basal and meal-stimulated acid secretion. ECL cells release histamine in response to gastrin, which then acts on parietal cell H2 receptors — H2 blockers thus also indirectly block gastrin-stimulated secretion. PPIs act downstream directly on the proton pump.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.