Sulfonylureas stimulate insulin secretion from pancreatic beta cells by which mechanism?

• A Binding to the SUR1 subunit of the ATP-sensitive potassium channel, causing channel closure and membrane depolarisation ✓
• B Activation of adenylyl cyclase through the GLP-1 receptor, raising intracellular cyclic AMP
• C Phosphorylation of the insulin receptor tyrosine kinase domain
• D Opening of voltage-gated potassium channels to shorten the action potential

Explanation

Sulfonylureas bind the SUR1 regulatory subunit of the beta-cell ATP-sensitive potassium channel. Closure of the channel depolarises the membrane, opens voltage-gated calcium channels and triggers insulin granule exocytosis. Because this occurs independently of ambient glucose, sulfonylureas carry a genuine risk of hypoglycaemia, unlike incretin-based agents whose secretion is glucose dependent. Option B is the DPP-4 inhibitor and GLP-1 agonist pathway.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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