Electrochemical detection of nitric oxide production in perfused pig coronary artery: Comparison of the performances of two electrochemical sensors

In situ direct measurement of nitric oxide (NO) in biological media is now possible by means of electrochemical detection. In the literature, there ar e principally two amperometric approaches based on the direct oxidation of NO either on a sensor made from platinum/ iridium (Pt/Ir) alloy coated with a three-layered membrane or on a nickel porphyrin and Nafion-coated carbon fiber electrode. Nonetheless, the exact nature of the experimental amperom etric signal obtained with the Pt/Ir system was never authenticated as bein g related to NO. This study compared responses of two sensors to the inhibi tion effect of N-omega-nitro-L-arginine (L-NA) as the amperometric signals produced by 5-hydroxytryptamine (5-HT) on isolated pig coronary preparation s. These amperometric signals could be attributed to NO only for the nickel porphyrin and Nafion-coated carbon fiber electrode. Indeed, voltammetric c haracterization of the electrochemical response demonstrated only variation s of the baseline current upon additions of either SNAP or NO on the Pt/Ir electrode instead of anodic peak current displayed at 0.63-0.75 V for the o ther system. Nitrites induced baseline current variations with the Pt/Ir el ectrode, similar to those obtained with S-nitroso-N-acetyl-dl-penicillamine (SNAP) or NO. This study highlights the potential hazards and pitfalls tha t may be associated with the use of a Pt/Ir sensor calibrated with SNAP sol utions for the detection of NO production in various biological systems. (C ) 1999 Elsevier Science Inc.