Fry E T, Mack D L, Monge J C, Billadello J J, Sobel B E
Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri 63110.
J Nucl Med. 1990 Feb;31(2):187-91.
Prompt detection of acute thrombosis and its response to treatment with thrombolytic agents generally require angiography. Scintigraphic approaches with labeled antibodies to or components of the coagulation and fibrinolytic systems have been disappointing because of prolonged circulating half-lives of tracers and relatively slow or limited binding to thrombi. Accordingly, we developed and characterized a thrombolytically inactive, active-site mutant (Ser-478----Thr) of tissue-type plasminogen activator (t-PA) designed to detect thrombi in vivo. Binding of iodine-125-(125I) labeled Ser----Thr t-PA to thrombi in vitro was time- and concentration-dependent, and specific judging from inhibition by pre-incubation with anti-t-PA IgG. Clearance of 125I-labeled mutant t-PA in rabbits was rapid and biexponential (alpha t1/2 = 1.9 +/- 0.4 min, beta t1/2 = 39.8 +/- 11.2 min). Thus, the amidolytically inactive mutant of t-PA designed binds rapidly and specifically to human thrombi in vitro and is cleared rapidly from the circulation in vivo--properties rendering it attractive as a potentially useful clot imaging agent.
急性血栓形成的快速检测及其对溶栓剂治疗的反应通常需要血管造影术。使用针对凝血和纤维蛋白溶解系统的抗体或其成分的闪烁成像方法一直不尽人意，原因是示踪剂的循环半衰期延长以及与血栓的结合相对缓慢或有限。因此，我们开发并鉴定了一种组织型纤溶酶原激活剂（t-PA）的溶栓无活性、活性位点突变体（Ser-478→Thr），旨在体内检测血栓。体外，碘-125（125I）标记的Ser→Thr t-PA与血栓的结合具有时间和浓度依赖性，并且从与抗t-PA IgG预孵育的抑制作用判断具有特异性。兔体内125I标记的突变体t-PA清除迅速且呈双指数性（α半衰期=1.9±0.4分钟，β半衰期=39.8±11.2分钟）。因此，所设计的t-PA酰胺水解无活性突变体在体外能快速、特异性地与人血栓结合，在体内能从循环中快速清除——这些特性使其作为一种潜在有用的血凝块成像剂具有吸引力。
