Can voltammetry measure nitrogen monoxide (NO) and/or nitrites?
Recently, voltammetry with carbon fibre electrodes (CFE) has been implemented for real time measurement of nitrogen monoxide (NO) indicating that it is oxidised at the potential value of nitrites, approximately +700 mV. In contrast, here we show that modified CFE can monitor NO at oxidation potentials different than that of nitrites, i.e. +550 mV. Indeed, at +550 mV a significant increase of amperometric current levels was obtained when NO but not nitrites, were added to a phosphate buffer saline solution (PBS). Differential pulse voltammetry (DPV) supports these findings as two oxidation peaks were obtained when examining air preserved NO; peak 1 at +550 mV and peak 2 at +700 mV, respectively. In contrast, only peak 2 was monitored when nitrites or a solution of NO oxidised in air was added to PBS. Biological support to these in vitro data comes from the observation that the relaxation of an adrenaline-contracted aortic ring produced via addition of NO is concomitant with peak 1 at +550 mV. The relaxation is almost completed before the appearance of peak 2 at +700 mV. Furthermore, in vivo experiments performed in the striatum of rats show that the amperometric signal monitored at +550 mV is responsive to glutamatergic stimulation or inhibition of NO synthase.
Crespi
F
F
Department of Biology, GlaxoWellcome S.p.A., Medicine Research Centre, via A. Fleming 4, 37135, Verona, Italy. fc20377@glaxowellcome.co.uk
Campagnola
M
M
Neudeck
A
A
McMillan
K
K
Rossetti
Z
Z
Pastorino
A
A
Garbin
U
U
Fratta-Pasini
A
A
Reggiani
A
A
Gaviraghi
G
G
Cominacini
L
L
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D002244:Carbon / Q000592:standards; D000077482:Carbon Fiber; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D008839:Microelectrodes / Q000592:standards / Q000639:trends*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D009448:Neurochemistry / Q000295:instrumentation / Q000379:methods*; D009569:Nitric Oxide / Q000032:analysis*; D009573:Nitrites / Q000032:analysis*; D051381:Rats; D017208:Rats, Wistar
D000077482:Carbon Fiber; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D009573:Nitrites; D009569:Nitric Oxide; D016202:N-Methylaspartate; D002244:Carbon; D015763:2-Amino-5-phosphonovalerate; D019331:NG-Nitroarginine Methyl Ester; D004837:Epinephrine