Aerts R J, Gillis K, Pannekoek H
Department of Molecular Biology, Central Laboratory of The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Thromb Haemost. 1989 Sep 29;62(2):699-703.
It has recently been shown that the fibrinolytic components plasminogen and tissue-type plasminogen activator (t-PA) both bind to cultured human umbilical vein endothelial cells (HUVEC). After cleavage of t-PA by plasmin, "single-chain" t-PA (sct-PA) is converted into "two-chain" t-PA (tct-PA), which differs from the former in a number of respects. We compared binding of sct-PA and tct-PA to the surface of HUVEC. Removal of t-PA bound to HUVEC by a mild treatment with acid and a subsequent quantification of eluted t-PA both by activity- and immunoradiometric assays revealed that, at concentrations between 10 and 500 nM, HUVEC bind about 3-4 times more sct-PA than tct-PA. At these concentrations, both sct-PA and tct-PA remain active when bound to HUVEC. Mutual competition experiments showed that sct-PA and tct-PA can virtually fully inhibit binding of each other to HUVEC, but that an about twofold higher concentration of tct-PA is required to prevent half-maximal binding of sct-PA than visa versa. These results demonstrate that sct-PA and tct-PA bind with different affinities to the same binding sites on HUVEC.
最近有研究表明，纤溶成分纤溶酶原和组织型纤溶酶原激活剂（t-PA）都能与培养的人脐静脉内皮细胞（HUVEC）结合。纤溶酶将t-PA裂解后，“单链”t-PA（sct-PA）转变为“双链”t-PA（tct-PA），二者在多个方面存在差异。我们比较了sct-PA和tct-PA与HUVEC表面的结合情况。通过温和的酸处理去除与HUVEC结合的t-PA，随后通过活性测定和免疫放射分析对洗脱的t-PA进行定量，结果显示，在10至500 nM的浓度范围内，HUVEC对sct-PA的结合量比对tct-PA的结合量多约3至4倍。在这些浓度下，sct-PA和tct-PA与HUVEC结合时均保持活性。相互竞争实验表明，sct-PA和tct-PA实际上可以完全抑制彼此与HUVEC的结合，但阻止sct-PA达到最大结合量一半时所需的tct-PA浓度约为阻止tct-PA达到最大结合量一半时所需sct-PA浓度的两倍。这些结果表明，sct-PA和tct-PA以不同的亲和力结合到HUVEC上的相同结合位点。
