Alevriadou B R, Moake J L, Turner N A, Ruggeri Z M, Folie B J, Phillips M D, Schreiber A B, Hrinda M E, McIntire L V
Cox Laboratory for Biomedical Engineering, Rice University, Houston, TX 77251.
Blood. 1993 Mar 1;81(5):1263-76.
Two likely mechanisms for the initiation of arterial platelet thrombus formation under conditions of elevated fluid shear stresses are: (1) excessive adhesion and aggregation of platelets from rapidly flowing blood onto the exposed sub-endothelium of injured, atherosclerotic arteries; or (2) direct, fluid shear stress-induced aggregation of platelets in constricted arteries with intact endothelial cells. Mechanism (1) was simulated using a parallel plate flow chamber, fibrillar collagen type I-coated slides, and mepacrine-labeled (fluorescent) platelets in whole blood anticoagulated with citrate, hirudin, unfractionated porcine heparin, or low molecular weight heparin flowing for 1 to 2 minutes at wall shear rates of 100 to 3,000 seconds-1 (4 to 120 dynes/cm2). The precise sequence of interactions among von Willebrand factor (vWF), glycoprotein (GP)Ib, and GPIIb-IIIa during platelet adhesion and subsequent aggregation were resolved by direct real-time observation using a computerized epifluorescence video microscopy system. Adhesion at high shear rates was the result of the adsorption of large vWF multimers onto collagen and the binding of platelet GPIb to the insolubilized vWF. Aggregation occurred subsequently and required the binding of ligands, including vWF via its RGD binding domain, to GPIIb-IIIa. Mechanism (2) was modeled by producing shear stresses of 90 to 180 dynes/cm2 in a rotational cone and plate viscometer, which aggregates platelets from platelet-rich-plasma (PRP) anti-coagulated with citrate, hirudin, or either type of heparin in reactions that require large vWF multimers, Ca2+, adenosine diphosphate, and both GPIb and GPIIb-IIIa. Both vWF-mediated shear-aggregation in PRP and platelet-collagen adhesion in flowing whole blood (anticoagulated with citrate and hirudin) are inhibited by two potentially useful anti-arterial thrombotic agents: polymeric aurin tricarboxylic acid (ATA; 28.5 to 114 micrograms/mL), which binds to vWF and inhibits its attachment of GPIb, and a recombinant vWF fragment (rvWF445-733; 30 to 200 micrograms/mL) that binds to platelet GPIb (in the absence of any modulator) and blocks attachment of vWF multimers. Unfractionated heparin, but not low molecular weight heparin, apparently binds to rvWF445-733 and counteracts the inhibitory effects of the vWF fragment in vitro on shear-aggregation and platelet-collagen adhesion.
在流体剪切应力升高的情况下，动脉血小板血栓形成起始的两种可能机制是：（1）快速流动的血液中的血小板过度黏附并聚集到受损的动脉粥样硬化动脉暴露的内皮下；或（2）在具有完整内皮细胞的狭窄动脉中，流体剪切应力直接诱导血小板聚集。机制（1）通过使用平行板流动腔、I型纤维状胶原包被的载玻片以及用柠檬酸盐、水蛭素、未分级猪肝素或低分子量肝素抗凝的全血中用米帕林标记（荧光）的血小板来模拟，在壁面剪切速率为100至3000秒⁻¹（4至120达因/平方厘米）的条件下流动1至2分钟。通过使用计算机化落射荧光视频显微镜系统进行直接实时观察，解析了血管性血友病因子（vWF）、糖蛋白（GP）Ib和GPIIb-IIIa在血小板黏附及随后聚集过程中相互作用的精确序列。高剪切速率下的黏附是由于大vWF多聚体吸附到胶原上以及血小板GPIb与不溶性vWF结合的结果。随后发生聚集，这需要包括vWF通过其RGD结合域在内的配体与GPIIb-IIIa结合。机制（2）通过在旋转锥板粘度计中产生90至180达因/平方厘米的剪切应力来模拟，该应力使富含血小板血浆（PRP）中的血小板聚集，PRP用柠檬酸盐、水蛭素或任何一种肝素抗凝，反应需要大vWF多聚体、Ca²⁺、二磷酸腺苷以及GPIb和GPIIb-IIIa。PRP中vWF介导的剪切聚集以及流动全血（用柠檬酸盐和水蛭素抗凝）中的血小板-胶原黏附均受到两种潜在有用的抗动脉血栓形成药物抑制：聚合金精三羧酸（ATA；28.5至114微克/毫升），其与vWF结合并抑制其与GPIb的附着，以及重组vWF片段（rvWF445-733；30至200微克/毫升），其与血小板GPIb结合（在没有任何调节剂的情况下）并阻断vWF多聚体附着。未分级肝素而非低分子量肝素显然与rvWF445-733结合，并在体外抵消vWF片段对剪切聚集和血小板-胶原黏附的抑制作用。
