Nitric oxide. A general review about the different roles of this innocent radical

Nitric oxide, a short half-life radical, is highly reactive, and it is involved in many biological processes, such as vascular homeostasis, neurotransmission, and inflammation, defined as a sequence of events which can be simplified as follows: vasodilatation, alteration of vascular permeability, emigration of leucocytes from vessels, migration of leucocytes into the sites of tissutal damages or inflammation, activation of leucocyte mechanisms. This review has a double purpose: 1) to provide a comprehensive table of cell types that produce NO, together with the effects of agents used to study iNOS regulation; 2) to investigate the role of NO in different human systems. The different relations between NO and cytokines, the heart, infectious diseases, inflammatory diseases, brain cells and, lastly, gastrointestinal diseases are examined.