Also known as nitrogen oxide, it is a free radical byproduct of combustion of substances in the air, as in automobile engines, fossil fuel power plants, and is produced naturally during the electrical discharges of lightning in thunderstorms. NO is an important cellular signaling molecule involved in many physiological and pathological processes. It is a powerful vasodilator with a short half life of a few seconds in the blood. Low levels of nitric oxide production are important in protecting organs such as the liver. Nitric oxide should not be confused with nitrous oxide (N2O), or nitrogen dioxide (NO2).
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