de Fouw N J, van Tilburg N H, Haverkate F, Bertina R M
IVVO-TNO, Gaubius Laboratorium, Leiden, The Netherlands.
Blood Coagul Fibrinolysis. 1993 Apr;4(2):201-10. doi: 10.1097/00001721-199304000-00001.
The effect of human activated protein C (APC) on t-PA dependent fibrinolysis was studied in vitro using plasma (and whole blood) clot lysis techniques. Clot lysis was monitored by measuring the release of soluble 125I-labelled fibrin degradation products from the clot over time. It was demonstrated that the stimulatory effect of APC on plasma and blood clot lysis was specific for APC and depended on the presence of its active site and Ca2+ ions. Furthermore, the effect depended on the presence of phospholipids in plasma or cells in blood. The presence of pro-urokinase, factor XIII or alpha 2-antiplasmin was not required for the expression of the profibrinolytic effect of APC. Subsequent experiments revealed that the profibrinolytic effect of APC was only observed when thrombin was formed through the coagulation pathway during the initial phase of the clot lysis experiment. It was also shown that the addition of increasing concentrations of thrombin itself could delay the t-PA dependent lysis of clots prepared from Al(OH)3 adsorbed plasma via a mechanism not yet understood. Based on these findings we propose that (a) t-PA dependent lysis of clots prepared from pooled normal plasma is delayed by thrombin generated through the coagulation system, and (b) that by its anticoagulant properties APC blocks this thrombin generation and thereby prevents the delay in clot lysis. Because in this model the profibrinolytic effect of APC is directly related to its anticoagulant properties we predicted and confirmed that other anticoagulants--like heparin--also have profibrinolytic activity. Conversely, procoagulants such as phospholipids can be antifibrinolytic.
采用血浆（和全血）凝块溶解技术，在体外研究了人活化蛋白C（APC）对组织型纤溶酶原激活剂（t-PA）依赖性纤维蛋白溶解的影响。通过测量可溶性125I标记的纤维蛋白降解产物随时间从凝块中的释放来监测凝块溶解。结果表明，APC对血浆和血凝块溶解的刺激作用是APC特有的，并且取决于其活性位点和Ca2+离子的存在。此外，该作用还取决于血浆中磷脂或血液中细胞的存在。APC促纤维蛋白溶解作用的表达不需要尿激酶原、因子 XIII 或α2-抗纤溶酶的存在。随后的实验表明，只有在凝块溶解实验初始阶段通过凝血途径形成凝血酶时，才观察到APC的促纤维蛋白溶解作用。还表明，添加浓度不断增加的凝血酶本身可通过一种尚未明确的机制延迟由氢氧化铝吸附血浆制备的凝块的t-PA依赖性溶解。基于这些发现，我们提出：（a）通过凝血系统产生的凝血酶会延迟由混合正常血浆制备的凝块的t-PA依赖性溶解；（b）APC通过其抗凝特性阻断这种凝血酶的产生，从而防止凝块溶解延迟。因为在该模型中，APC的促纤维蛋白溶解作用与其抗凝特性直接相关，所以我们预测并证实其他抗凝剂（如肝素）也具有促纤维蛋白溶解活性。相反，促凝剂如磷脂可具有抗纤维蛋白溶解作用。
