Atrial natriuretic peptide lowers blood pressure by causing renal sodium excretion and vascular smooth muscle relaxation. The second messenger system engaged by the ANP receptor is:

• A cGMP generated by a receptor that itself possesses guanylyl cyclase activity ✓
• B cAMP generated through a Gs-coupled mechanism
• C Inositol trisphosphate released by receptor-associated phospholipase C
• D Nitric oxide diffusing into the cell to activate cytosolic guanylyl cyclase

Explanation

The ANP receptor is a single-pass membrane protein whose intracellular domain is itself a particulate guanylyl cyclase. Ligand binding converts GTP to cGMP within the same receptor molecule, and cGMP activates protein kinase G, producing natriuresis and vasodilation. Option D describes endothelium-derived nitric oxide activating soluble guanylyl cyclase, a separate pathway that shares the same second messenger but is receptor independent. Options B and C describe classical GPCR pathways not used by ANP.

Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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