MS-0446

A 48-year-old man visits his local doctor complaining of chest pain that occurs during physical activity and subsides with rest. He first noticed it 10 months ago and feels that it has gradually worsened. He now experiences this pain while climbing a few stairs. Previously, he could walk down to the newsagent and back, a distance of 200 yards, without any discomfort. He has a medical history of hypertension and appendectomy.

His close friend had similar symptoms that were relieved by sublingual glyceryl nitrates. He asks the doctor to prescribe something similar.

What is the mechanism by which nitrates work?