Definition:

Nitric oxide (NO) is a gas with diverse biological activities produced from arginine by NO synthases. It is capable of interacting with a number of molecules, most notably superoxide, forming peroxynitrite, which, in turn, can mediate bactericidal or cytotoxic reactions. Nitric oxide also mediates smooth muscle relaxation, neurotransmission, and modulation of inflammation in a number of organ systems and pathophysiologic conditions.