Kuppusamy P, Wang P, Zweier J L, Krishna M C, Mitchell J B, Ma L, Trimble C E, Hsia C J
Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA.
Biochemistry. 1996 Jun 4;35(22):7051-7. doi: 10.1021/bi952857s.
Electron paramagnetic resonance (EPR) imaging utilizing stable nitroxyl radicals is a promising technique for measuring free radical distribution, metabolism, and tissue oxygenation in organs and tissues [Kuppusamy, P., Chzhan, M., Vij, K., Shteynbuk, M., Lefer, D. J., Giannella, E., & Zweier, J. L. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 3388-3392]. However, the technique has been limited by the rapid reduction of nitroxide in vivo to its hydroxylamine derivative, a diamagnetic, EPR-inactive species. In this report a novel, polynitroxylated derivative of human serum albumin is shown to be capable of reoxidizing the hydroxylamine back to nitroxide in vivo. Polynitroxyl-albumin (PNA) is shown to be effective in maintaining the signal intensity of the nitroxide 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL or TPL) in the ischemic isolated rat heart, allowing the acquisition of high-resolution three-dimensional (3D) EPR images of the heart throughout a prolonged 2.5 h period of global cardiac ischemia. In serial transverse sections of the 3D image, TPL intensity maps of the heart showed cardiac structure with submillimeter resolution. TPL intensities in coronary arteries and myocardium showed that nitroxide concentration decreases with increasing distance from large blood vessels. These results demonstrate that EPR imaging in vivo is possible using nitroxides in conjunction with PNA. In addition to its utility in the emerging technology of EPR imaging, the greatly prolonged half-life of TPL observed in the presence of PNA may facilitate the therapeutic application of nitroxides in a variety of disease processes.
利用稳定的硝酰自由基进行电子顺磁共振（EPR）成像，是一种用于测量器官和组织中自由基分布、代谢及组织氧合的很有前景的技术[库普萨米，P.，奇赞，M.，维杰，K.，什泰恩布克，M.，勒费尔，D. J.，詹内拉，E.，& 茨韦尔，J. L.（1994年）《美国国家科学院院刊》91，3388 - 3392]。然而，该技术一直受到体内硝氧化物迅速还原为其羟胺衍生物（一种抗磁性的、EPR无活性的物质）的限制。在本报告中，一种新型的人血清白蛋白多硝酰化衍生物被证明能够在体内将羟胺重新氧化回硝氧化物。多硝酰白蛋白（PNA）被证明在维持缺血离体大鼠心脏中硝氧化物4 - 羟基 - 2,2,6,6 - 四甲基哌啶 - 1 - 氧基（TEMPOL或TPL）的信号强度方面是有效的，从而能够在长达2.5小时的全心缺血期间获取心脏的高分辨率三维（3D）EPR图像。在3D图像的连续横切面上，心脏的TPL强度图显示出具有亚毫米分辨率的心脏结构。冠状动脉和心肌中的TPL强度表明，硝氧化物浓度随着与大血管距离的增加而降低。这些结果表明，结合PNA使用硝氧化物进行体内EPR成像是可行的。除了在新兴的EPR成像技术中的应用外，在PNA存在下观察到的TPL半衰期大大延长，可能有助于硝氧化物在各种疾病过程中的治疗应用。
