A patient is prescribed ranitidine (H2 blocker) for peptic ulcer. H2 blockers reduce acid secretion by blocking histamine action on which cell?

• A G cells of antrum
• B Chief cells secreting pepsinogen
• C Enterochromaffin-like cells releasing histamine
• D Parietal cells of gastric body ✓

Explanation

Parietal (oxyntic) cells of the gastric body and fundus are the site of acid (HCl) secretion, mediated by H+/K+-ATPase. These cells have H2, muscarinic M3, and gastrin CCK-B receptors; stimulation of any receptor activates the final common pathway — the proton pump. Ranitidine competitively and selectively blocks H2 receptors on parietal cells, reducing basal and stimulated acid secretion by approximately 70%, particularly nocturnal acid output which depends heavily on histamine.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.