Exhaled nitric oxide as a marker for organic nitrate tolerance

Abstract

Background This study was designed to demonstrate the development of biochemical tolerance to organic nitrates by measuring levels of exhaled gaseous nitric oxide (NO) in lambs given intravenous (IV) nitroglycerin or sodium nitroprusside. Methods and Results IV injections of nitroglycerin or sodium nitroprusside produced dose-dependent and sustained increases in the exhaled levels of nitric oxide measured by chemiluminescence in awake lambs with tracheostomies. After a 6-hour IV infusion of 25 μg · kg-1 · min-1 nitroglycerin, peak exhaled NO levels were significantly reduced (- 53.6±4.9%, mean±SEM, P