Reszka Krzysztof J, McCormick Michael L, Buettner Garry R, Hart C Michael, Britigan Bradley E
VA Medical Center-Cincinnati, OH, USA.
Nitric Oxide. 2006 Sep;15(2):133-41. doi: 10.1016/j.niox.2006.03.004. Epub 2006 May 2.
The effect nitric oxide (NO*) on the stability of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) adducts has been investigated using EPR spectroscopy. We report that the DMPO/HO* adduct, generated by porcine pulmonary artery endothelial cells in the presence of H2O2 and DMPO, or by a Fenton system (Fe(II)+H2O2) is degraded in the presence of the NO*-donor, 2-(N,N-diethylamino)-diazenolate-2-oxide (DEANO) or by bolus addition of an aqueous solution of NO*. A similar effect of DEANO was observed on other DMPO adducts, such as DMPO/CH3 and DMPO/CH(CH3)OH, generated in cell-free systems. Measurements of the loss of DMPO/HO in the presence of DEANO in aerated and oxygen-free buffers showed that in both of these settings the process obeys first-order kinetics and proceeds with similar efficacy. This indicates that direct interaction of the nitroxide with NO, rather than with NO2* (formed from NO* and O2 in aerated media), is responsible for destruction of the spin adduct. These results suggest that the presence of NO* may substantially affect the quantitative determination of DMPO adducts. We also show that NO2* radicals, generated by a myeloperoxidase/H2O2/nitrite system, also degrade DMPO/HO*. Because DMPO is frequently used to study generation of superoxide and hydroxyl radicals in biological systems, these observations indicate that extra caution is required when studying generation of these species in the presence of NO* or NO2* radicals.
利用电子顺磁共振波谱法研究了一氧化氮（NO*）对5,5-二甲基-1-吡咯啉-N-氧化物（DMPO）加合物稳定性的影响。我们报告称，在过氧化氢和DMPO存在的情况下，由猪肺动脉内皮细胞产生的DMPO/HO加合物，或由芬顿体系（Fe(II)+H2O2）产生的该加合物，在NO供体2-(N,N-二乙氨基)-重氮酸-2-氧化物（DEANO）存在时或通过一次性添加NO水溶液会发生降解。在无细胞体系中产生的其他DMPO加合物，如DMPO/CH3和DMPO/CH(CH3)OH，也观察到了DEANO的类似作用。在通气和无氧缓冲液中存在DEANO的情况下对DMPO/HO损失的测量表明，在这两种情况下该过程均符合一级动力学，且降解效率相似。这表明氮氧化物与NO的直接相互作用，而非与（在通气介质中由NO和O2形成的）NO2的相互作用，是导致自旋加合物破坏的原因。这些结果表明，NO的存在可能会显著影响DMPO加合物的定量测定。我们还表明，由髓过氧化物酶/H2O2/亚硝酸盐体系产生的NO2自由基也会降解DMPO/HO。由于DMPO经常用于研究生物体系中超氧化物和羟基自由基的产生，这些观察结果表明，在存在NO或NO2自由基的情况下研究这些物种的产生时需要格外小心。
