ADH acting on the collecting duct inserts functional water channels into the apical membrane. Which receptor and second messenger mediate this effect?

• A V1 receptor coupled to phospholipase C and calcium
• B Aquaporin-1 receptor coupled to guanylate cyclase and cGMP
• C V2 receptor coupled to phospholipase C and diacylglycerol
• D V2 receptor coupled to adenylate cyclase, cAMP, and PKA-dependent trafficking of aquaporin-2 ✓

Explanation

ADH binds V2 receptors on the basolateral membrane of collecting duct principal cells. The V2 receptor is Gs-coupled, raising cAMP and activating protein kinase A, which phosphorylates aquaporin-2 and promotes fusion of its storage vesicles with the apical membrane, increasing water permeability. The V1 receptor uses phospholipase C and calcium and mediates vasoconstriction, not antidiuresis. Aquaporin-1 is constitutively active in the proximal tubule and descending limb and is not ADH regulated.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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