Direct measurement of nitric oxide in human beings.

Nitric oxide is a short-lived radical involved in various biological processes. We have used an electrochemical microsensor to detect nitric oxide signals in blood vessels of healthy volunteers. The sensor was inserted into a hand vein, and the vessel was stimulated with acetylcholine or bradykinin. Dose-dependent signals were detected and were attenuated by an inhibitor of nitric oxide synthase. The results provide further evidence that endothelium-derived relaxing factor is nitric oxide and demonstrate a method for monitoring the L-arginine/nitric-oxide pathway in human beings.