Endothelial nitric oxide synthase (eNOS) in platelets: how is it regulated and what is it doing there?

Platelets express the endothelial form of the nitric oxide synthase (eNOS) and generate NO. However, in contrast to eNOS in endothelial cells, eNOS in platelets is largely Ca(2+)-independent and the activity is regulated by phosphorylation. Platelet-derived NO plays an important role in the regulation of platelet aggregation and secretion. Changes in the activity of platelet eNOS are responsible for the abnormal platelet activation encountered in different pathological situations (e.g. hypertension and diabetes). In this review, we will summarize the current knowledge of the role of platelet eNOS and the regulation of its activity as well as the fate of platelet-derived NO in physiological and pathological situations.