■ Advantages and limits of the electrochemical method using Nafion and Ni-porphyrin-coated microelectrode to monitor NO release from cultured vascular cells

Electrochemical monitoring with a porphyrinic microsensor of in situ nitric oxide production from cultured cells offers numerous advantages but requires cautious analysis, repeated calibration and accurate localisation of the electrode. It also had some limitations. We describe here some characteristics of this method, the stability of the electrode response during experiments and its application to nitric oxide production by constitutive and inducible nitric oxide synthases. Real-time measurements of NO concentration allow the study of the kinetics of NO production. This is illustrated by the time-course of NO release from cultured human endothelial cells. How NO production by inducible nitric oxide synthase in cultured smooth muscle cells obtained from human internal mammary artery can be evaluated by Nafion- and Ni-porphyrin-coated electrode is also described. The results thus obtained are compared to the cumulated NO 2 - production evaluated by the Griess method.