Hantgan R R, Hindriks G, Taylor R G, Sixma J J, de Groot P G
Department of Biochemistry, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27103.
Blood. 1990 Jul 15;76(2):345-53.
We have investigated the molecular basis of thrombus formation by measuring the extent of platelet deposition from flowing whole blood onto fibrin-coated glass coverslips under well-defined shear conditions in a rectangular perfusion chamber. Platelets readily and specifically adhered to fibrin-coated coverslips in 5 minute perfusion experiments done at either low (300 s-1) or high (1,300 s-1) wall shear rates. Scanning electron microscopic examination of fibrin-coated coverslips after perfusions showed surface coverage by a monolayer of adherent, partly spread platelets. Platelet adhesion to fibrin was effectively inhibited by a monoclonal antibody (MoAb) specific for glycoprotein (GP) IIb:IIIa. The dose-response curve for inhibition of adhesion by anti-GPIIb:IIIa at both shear rates paralleled that for inhibition of platelet aggregation. Platelet aggregation and adhesion to fibrin were also blocked by low concentrations of prostacyclin. In contrast, anti-GPIb reduced adhesion by 40% at 300 s-1 and by 70% at 1,300 s-1. A similar pattern of shear rate-dependent, incomplete inhibition resulted with a MoAb specific for the GPIb-recognition region of von Willebrand factor (vWF). Platelets from an individual with severe von Willebrand's disease, whose plasma and platelets contained essentially no vWF, exhibited defective adhesion to fibrin, especially at the higher shear rate. Addition of purified vWF restored adhesion to normal values. These results are consistent with a two-site model for platelet adhesion to fibrin, in which the GPIIb:IIIa complex is the primary receptor, with GPIb:vWF providing a secondary adhesion pathway that is especially important at high wall shear rates.
我们通过在矩形灌注室中明确的剪切条件下，测量全血在流经纤维蛋白包被的玻璃盖玻片时血小板沉积的程度，研究了血栓形成的分子基础。在低（300 s-1）或高（1300 s-1）壁剪切速率下进行的5分钟灌注实验中，血小板很容易且特异性地黏附于纤维蛋白包被的盖玻片上。灌注后对纤维蛋白包被的盖玻片进行扫描电子显微镜检查，结果显示表面被单层黏附的、部分铺展的血小板覆盖。一种针对糖蛋白（GP）IIb:IIIa的单克隆抗体（MoAb）可有效抑制血小板与纤维蛋白的黏附。在两种剪切速率下，抗GPIIb:IIIa抑制黏附的剂量反应曲线与抑制血小板聚集的曲线平行。低浓度的前列环素也可阻断血小板聚集及与纤维蛋白的黏附。相比之下，抗GPIb在300 s-1时使黏附减少40%，在1300 s-1时使黏附减少70%。针对血管性血友病因子（vWF）的GPIb识别区域的MoAb也产生了类似的剪切速率依赖性、不完全抑制模式。一名患有严重血管性血友病的个体，其血浆和血小板中基本不含vWF，该个体的血小板对纤维蛋白的黏附存在缺陷，尤其是在较高剪切速率下。添加纯化的vWF可使黏附恢复至正常水平。这些结果与血小板黏附于纤维蛋白的双位点模型一致，其中GPIIb:IIIa复合物是主要受体，GPIb:vWF提供次要黏附途径，该途径在高壁剪切速率下尤为重要。
