Couet W R, Brasch R C, Sosnovsky G, Tozer T N
Magn Reson Imaging. 1985;3(1):83-8. doi: 10.1016/0730-725x(85)90012-8.
Because of their paramagnetic properties, nitroxides are potentially useful as contrast agents in magnetic resonance imaging (MRI). They are reduced in vivo to their corresponding hydroxylamines which are nonparamagnetic and have no contrast enhancing property. Nitroxides with high resistance to reduction would be advantageous as pharmaceutical contrast enhancing agents. We show that in the presence of ascorbic acid and in tissue homogenates, the reduction is faster for piperidine than for pyrrolidine nitroxides and for positively-charged than for negatively-charged derivatives. The data also suggest that nitroxide reduction in tissue homogenates is mainly due to sulfhydryl groups on proteins and that endogenous ascorbic acid plays a relatively minor role.
由于具有顺磁特性，氮氧化物在磁共振成像（MRI）中有可能用作造影剂。它们在体内被还原为相应的羟胺，而羟胺是抗磁性的，没有造影增强特性。对还原具有高抗性的氮氧化物作为药物造影增强剂将具有优势。我们表明，在抗坏血酸存在的情况下以及在组织匀浆中，哌啶氮氧化物的还原速度比吡咯烷氮氧化物快，带正电荷的衍生物比带负电荷的衍生物还原速度快。数据还表明，组织匀浆中的氮氧化物还原主要是由于蛋白质上的巯基，而内源性抗坏血酸起的作用相对较小。
