Nitric Oxide Signaling in Platelets

Nitric oxide was recognized fifteen years ago to be an endothelium-dependent relaxing factor with an important role in vasomotor control through its actions on vascular smooth muscle (1 ). Shortly after this discovery it was also demonstrated that nitric oxide (NO) is an inhibitor of platelet function and plays a physiological role in the reduction in platelet activation (2 ). This is achieved because platelets while circulating, being the smallest of the blood cells, are closest to the endothelium, which is considered to be the most important source of NO in the vasculature. However, it was soon realized that platelets themselves are capable of biosynthesising NO when they are activated (3 ).