Nitric Oxide

Nitric Oxide: "Nitric oxide (NO) is an important signalling molecule that acts in many tissues to regulate a diverse range of physiological processes. It's role was first discovered by several groups who were attempting to identify the agent responsible for promoting blood vessel relaxation and regulating vascular tone. This agent was termed endothelium-derived relaxing factor (EDRF), and was initially assumed to be a protein like most other signalling molecules. The discovery that EDRF was in fact nitric oxide - a small gaseous molecule - has led to an explosion of interest in this field and resulted in many thousands of publications over the last few years. Nitric oxide has now been demonstrated to play a role in a variety of biological processes including neurotransmission, immune defence, the regulation of cell death (apoptosis). Nitric oxide is a fairly short-lived molecule (with a half-life of a few seconds) produced from enzymes known as nitric oxide synthases (NOS).

Since it is such a small molecule NO is able to diffuse rapidly across cell membranes and, depending on the conditions, is able to diffuse distances of more than several hundred microns. The biological effects of NO are mediated through the reaction of NO with a number of targets such as haem groups, sulfhydryl groups and iron and zinc clusters. Such a diverse range of potential targets for NO explains the large number of systems that utilise it as a regulatory molecule. As a consequence of this abnormal regulation or control of NO synthesis is capable of affecting a number of important biological processes and has been implicated in a variety of diseases."