A 53-year-old man arrives at the emergency room complaining of shortness of breath and chest tightness. When the patient's symptoms first appeared, he was participating in a poker tournament. He has a history of hypertension and is not taking his medications as prescribed. His last medical check-up was over a year ago. The blood pressure is 195/115 mm Hg, and the pulse rate is 90 beats per minute. Bibasilar crackles are discovered during a lung examination. A nitroglycerin infusion is started, which results in significant symptom relief. The repeat blood pressure reading is 165/90 mm Hg. Which of the following intracellular events is most likely responsible for the beneficial effects of this patient's treatment?

Question

Quizplus · Accepted Answer

Eductional Objective: The clinical presentation of this patient is consistent with acute pulmonary edema caused by severely elevated blood pressure (hypertensive emergency). Intravenous vasodilators (nitroglycerine, sodium nitroprusside) are frequently used in such cases to improve acute heart failure by lowering preload and afterload.
Within vascular smooth muscle cells, nitrates are converted to nitric oxide, which activates guanylate cyclase and promotes the conversion of guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP). Increased cGMP levels result in decreased intracellular calcium (reduces myosin light-chain kinase activity) and activation of myosin light chain phosphatase. This promotes dephosphorylation of myosin light chains and relaxation of vascular smooth muscle.

A 53-Year-Old Man Arrives at the Emergency Room Complaining of Shortness