NO release from NO donors and nitrovasodilators: Comparisons between oxyhemoglobin and potentiometric assays

Unraveling the biology, pharmacology, and toxicology of NO depends on accurate NO assays, two of the more common being the oxyHb (oxyhemoglobin) assay and potentiometric detection using a Clark-type NO-selective electrode. Comparison of the specificity and sensitivity of the oxyHb and potentiometric methods was carried out using a broad series of nitrovasodilators, including organic nitrates, nitrites, thionitrates, nitrosothiols, and diazenium diolates. Only with the more labile diazenium diolates was a linear relationship observed between the rates of NO release measured potentiometrically and the rate of oxyHb oxidation from the oxyHb assay. The nonlinear plots indicate that N,O-species other than NO itself are capable of oxidizing oxyHb.