What is Nitric Oxide?

Nitric Oxide, abbreviated as NO or N.O., is a molecule that is naturally produced in human biological function. Also known as nitrogen monoxide, it can additionally be found as a byproduct from combustion of fuel in the presence of oxygen. It is comprised of one atom of nitrogen and one atom of oxygen, and at standard temperature and pressure it is a gas. Scientists have discovered two ways that our bodies create NO. 


The most direct route is that of the nitrate-nitrite-nitric oxide pathway. Dietary nitrate is made of up one nitrogen atom and three oxygen atoms. Beet root, spinach, and Arugula are high in nitrate. Bacteria in our mouth, saliva, and upper gastrointestinal tract enzymatically reduce dietary nitrate which releases one of the oxygen atoms leaving us with nitrite. Nitrite is made up of one nitrogen atom and two oxygen atoms. Nitrite is reduced again by many pathways such as the acidic environment of our stomach, hemoglobin in our blood, or enzymes such as cytochrome P450 and Xanthine oxidoreductase, releasing another oxygen atom(Lundberg, et.al). This leaves us with nitric oxide which is made up of one nitrogen atom and one oxygen atom. 


The second route is the Nitric Oxide Synthase (NOS) pathway that occurs in many different cells in the body such as endothelial or neuronal cells. Starting with L-Arginine and oxygen, 5 electrons are exchanged with co-factors in a complicated enzymatic reaction yielding L-citrulline and NO. 


1. 2004 Jul;2(7):593-602. Lundberg JO, Weitzberg E, Cole JA, Benjamin N.