A patient with stable angina uses sublingual glyceryl trinitrate (GTN). The MAIN mechanism by which GTN reduces preload is:

• A Arterial vasoconstriction reducing afterload
• B Direct stimulation of beta-2 adrenergic receptors on venous smooth muscle
• C Conversion to nitric oxide activating guanylyl cyclase, increasing cGMP causing venodilation ✓
• D Blockade of L-type calcium channels in venous walls

Explanation

Organic nitrates like GTN undergo bioactivation to release nitric oxide (NO), which activates soluble guanylyl cyclase, increasing intracellular cGMP. cGMP activates protein kinase G, reducing intracellular calcium and causing smooth muscle relaxation. Nitrates preferentially dilate venous capacitance vessels at low doses, reducing venous return (preload) and thereby decreasing myocardial oxygen demand.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.