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首页> 外文期刊>Thrombosis and Haemostasis: Journal of the International Society on Thrombosis and Haemostasis >Ristocetin- and thrombin-induced platelet aggregation at physiological shear rates: differential roles for GPIb and GPIIb-IIIa receptor.
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Ristocetin- and thrombin-induced platelet aggregation at physiological shear rates: differential roles for GPIb and GPIIb-IIIa receptor.

机译：生理性剪切速率下的瑞斯托菌素和凝血酶诱导的血小板凝集：GPIb和GPIIb-IIIa受体的不同作用。

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We recently reported that washed platelets (WP) activated with ADP and expressing surface-bound vWF aggregated in flow through small tubes or in a cylindrical couette device at physiological shear rates of G = 300 s(-1)-1000 s(-1) in the absence of exogenous ligands, with GPIb-vWF partially, and activated GPIIb-IIIa totally required for the aggregation. We have now extended these studies to aggregation of platelets "activated" with ristocetin or thrombin. Washed platelet suspensions with added soluble vWF and ristocetin (0.3-0.75 mg/ml), or activated with thrombin (0.01-0.5 U/ml) but no added ligand, were sheared in a coaxial cylinder device at uniform shear rate, G = 1000 s(-1). The collision capture efficiency (alphaG) with which small aggregates form (= experimental/calculated initial rates of aggregation) was correlated with vWF platelet binding assessed by flow cytometry. The vWF-GPIb interaction was exclusively able to support ristocetin-mediated shear aggregation of metabolically active platelets, with very few vWF monomer equivalents bound per platelet (representing < or = 10 molecules of 10 million Da) required to yield high capture efficiencies (alphaG = 0.38+/-.02; n = 11), suggesting rapid and stable bond formations between vWF and GPIb. However, platelet surface-expressed vWF, generated by addition of thrombin to washed platelets, was found to mediate platelet aggregation with alphaG = 0.08+/-.01 (n = 6), surprisingly comparable to that previously reported for WP and ADP activation. Blocking the GPIIb-Illa receptor decreased alphaG by 95+/-3% (n =3), while a monoclonal antibody to the vWF site on GPIb caused a 49+/-7% (n = 8) decrease in alphaG. The partial role for GPIb thus appears to reflect a facilitative function for increasing contact time between flowing platelets, and allowing engagement of the GPIIb-IIa receptor to yield stable attachment.
机译：最近，我们报道了用ADP活化并表达表面结合的vWF的洗涤后的血小板（WP），其在生理学上的剪切速率为G = 300 s（-1）-1000 s（-1）的小管或圆柱形couette设备中聚集。在没有外源性配体的情况下，部分聚集了GPIb-vWF，并活化了聚集所需的GPIIb-IIIa。现在，我们将这些研究扩展到了被瑞斯托菌素或凝血酶“激活”的血小板聚集。加入同轴vWF和ristocetin（0.3-0.75 mg / ml）或用凝血酶（0.01-0.5 U / ml）活化但未添加配体的洗涤后的血小板悬浮液在同轴圆柱设备中以均匀剪切速率剪切，G = 1000 s（-1）。小聚集体形成的碰撞捕获效率（alphaG）（=实验/计算的初始聚集速率）与通过流式细胞仪评估的vWF血小板结合相关。 vWF-GPIb相互作用完全能够支持瑞斯托霉素介导的代谢活性血小板的剪切聚集，每个血小板结合的vWF单体当量很少（代表<或= 10个分子的一千万Da），产生高捕获效率（alphaG = 0.38 +/-。02; n = 11），表明vWF和GPIb之间快速而稳定地形成了键。然而，发现通过向洗涤过的血小板中添加凝血酶而产生的血小板表面表达vWF介导的血小板凝集具有alphaG = 0.08 +/-。01（n = 6），这与先前报道的WP和ADP活化令人惊讶地相当。阻断GPIIb-IIIa受体可使alphaG降低95 +/- 3％（n = 3），而针对GPIb上vWF位点的单克隆抗体导致alphaG降低49 +/- 7％（n = 8）。因此，GPIb的部分作用似乎反映出促进流动的血小板之间的接触时间增加并允许GPIIb-IIa受体接合以产生稳定附着的促进功能。

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