Haskel E J, Eisenberg P R, Abendschein D R
Cardiovascular Division, Washington University School of Medicine, St Louis, MO 63110.
Blood Coagul Fibrinolysis. 1993 Feb;4(1):7-13.
To characterize potential mechanisms for enhanced thrombolysis in the presence of thrombin inhibitors, we measured lysis of 125I-fibrin-(ogen)- labelled clots after incubation in rotating tubes with whole blood containing tissue-type plasminogen activator (t-PA, 1500 ng/ml) and either saline or increasing concentrations of recombinant desulphatohirudin (hirudin), or heparin. Thrombin activity in washed clots was negligible, but incubation of clots with t-PA in non-anticoagulated blood resulted in marked thrombin activity within 5 min as measured by fibrinopeptide A generation. Incubation with hirudin over a range of concentrations increased clot lysis compared with t-PA alone (control) from 132 +/- 18% of control with 0.5 microgram/ml (n = 4) to 216 +/- 48% of control with 10 micrograms/ml (n = 4). Incubation with less than 0.5 U/ml of heparin attenuated clot lysis (35 +/- 22% of control with 0.08 U/ml, n = 3) while concentrations > or = 0.5 U/ml increased lysis (178 +/- 13% of control with 1.7 U/ml, n = 4). Similar results were obtained for incubations in recalcified platelet-poor plasma indicating that platelets are not required for the enhancement of clot lysis induced by thrombin inhibitors. However, incubations in recalcified plasma from a patient with afibrinogenaemia abolished the increased lysis observed with 10 micrograms/ml of hirudin and addition of physiological concentrations of fibrin monomer (400-800 nM) or fibrinogen degradation products (500 nM) to the mixture of whole blood, t-PA and hirudin blunted the extent of clot lysis. Thus, inhibition of thrombin activity induced by exposure of clots to t-PA prevents concomitant formation of fibrin that attenuates fibrinolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
为了阐明在存在凝血酶抑制剂的情况下增强溶栓作用的潜在机制，我们在旋转管中用含有组织型纤溶酶原激活剂（t-PA，1500 ng/ml）以及生理盐水或浓度递增的重组去硫酸水蛭素（水蛭素）或肝素的全血孵育后，测定了125I-纤维蛋白-（原）标记凝块的溶解情况。洗涤后的凝块中凝血酶活性可忽略不计，但在未抗凝血液中用t-PA孵育凝块会导致5分钟内出现显著的凝血酶活性，这可通过纤维蛋白肽A的生成来测定。与单独使用t-PA（对照）相比，在一系列浓度下用水蛭素孵育可增加凝块溶解，从0.5微克/毫升时为对照的132±18%（n = 4）增加到10微克/毫升时为对照的216±48%（n = 4）。用低于0.5 U/ml的肝素孵育会减弱凝块溶解（0.08 U/ml时为对照的35±22%，n = 3），而浓度≥0.5 U/ml则会增加溶解（1.7 U/ml时为对照的178±13%，n = 4）。在重新钙化的少血小板血浆中孵育也得到了类似结果，表明血小板对于凝血酶抑制剂诱导的凝块溶解增强并非必需。然而，在无纤维蛋白原血症患者的重新钙化血浆中孵育消除了用10微克/毫升水蛭素观察到的溶解增加，并且向全血、t-PA和水蛭素的混合物中添加生理浓度的纤维蛋白单体（400 - 800 nM）或纤维蛋白原降解产物（500 nM）会减弱凝块溶解程度。因此，抑制凝块暴露于t-PA诱导的凝血酶活性可防止同时形成减弱纤维蛋白溶解的纤维蛋白。（摘要截断于250字）
