Misoprostol protects the gastric mucosa. Which prostaglandin receptor does it act on, and by what mechanism?

• A EP2 and EP4 receptors, increasing cAMP and stimulating mucus and bicarbonate secretion
• B TP receptors on gastric parietal cells, reducing TXA2-mediated acid hypersecretion
• C EP3 receptor (primarily), inhibiting adenylyl cyclase in parietal cells to reduce acid secretion, and EP1/EP3 receptors to stimulate mucus and bicarbonate ✓
• D IP receptors, causing mucosal vasodilation and increasing blood flow to the stomach

Explanation

Misoprostol is a synthetic PGE1 analogue. It acts on EP3 receptors on gastric parietal cells, which couple to Gi, reducing cAMP and thereby reducing acid secretion (antisecretory effect). It also acts on EP1 and EP3 receptors on mucous neck cells to stimulate mucus and bicarbonate secretion, and promotes mucosal blood flow (cytoprotective effects). These combined actions explain its utility in NSAID-induced ulcer prevention (NSAIDs deplete endogenous PGE2 by inhibiting COX). Misoprostol also acts on uterine EP3/EP1 receptors to cause myometrial contractions, explaining its use in cervical ripening and PPH management.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.