Exhaled nitric oxide after inhalation of isotonic and hypotonic solutions

Up to few years ago nitric oxide (NO), produced by several cells in the respiratory tract, was considered only a noxious gaseous component of environmental pollution it is involved in important biological roles including the regulation of blood flow, platelet function, neurotransmission and immunity. NO measurement from exhaled air has been suggested as a useful tool in monitoring inflammatory diseases in the human airways. NO detected in the airways may be influenced by several direct and indirect challenges, such as inhalation of solutions at different osmolarity. After a short review of NO chemical-physical property, production and physiology, the potential role of modifications of airway environment (osmolarity, pH, active and passive smoke) on mechanisms of NO synthesis and the relative physiopathological implications will be discussed.