Purvis N B, Giorgio T D
Department of Chemical Engineering, Vanderbilt University, Nashville, TN 37027.
Biorheology. 1991;28(5):355-67. doi: 10.3233/bir-1991-28501.
Hemodynamic shear is known to stimulate blood and endothelial cells and induce platelet activation. Many studies of shear-induced platelet stimulation have employed rotational viscometers in which secondary flow effects are assumed to be negligible. Shear induced platelet activation occurs at elevated shear rates where secondary flows may contribute a significant percentage of the total hydrodynamic force experienced by the sample. Elongational stress, one component of this secondary flow, has been shown to alter transmembrane ion flux in intact cell and the permeability of synthetic membrane preparations. Elongational flow also occurs in the vasculature at sites of elevated shear stress. Secondary flow components may contribute to platelet activation induced during shear stress application in rotational viscometry. A unique 'constrained convergence' elongational flow chamber was designed and fabricated to study platelet response to elongational stress exposure. The elongational flow chamber was capable of producing an elongation rate of 2.1 s-1 with a corresponding volume averaged shear rate of 58.33 s-1. Significant changes were observed in the total platelet volume distribution and measured response to added chemical antagonists after elongational stress exposure. The total platelet volume histogram shifted toward larger particle sizes, suggesting the formation of large aggregates as a result of elongational stress exposure. Platelets exposed to elongational stress demonstrated a dose dependent decrease in added ADP-induced aggregation rate and extent of aggregation.
已知血流动力学剪切力可刺激血液和内皮细胞并诱导血小板活化。许多关于剪切力诱导血小板刺激的研究都采用了旋转粘度计，其中假定二次流效应可忽略不计。剪切力诱导的血小板活化发生在较高的剪切速率下，此时二次流可能占样品所经历的总流体动力的很大比例。拉伸应力是这种二次流的一个组成部分，已被证明会改变完整细胞中的跨膜离子通量以及合成膜制剂的通透性。拉伸流也发生在剪切应力升高部位的脉管系统中。二次流成分可能有助于在旋转粘度测定中施加剪切应力期间诱导的血小板活化。设计并制造了一种独特的“受限收敛”拉伸流室，以研究血小板对拉伸应力暴露的反应。该拉伸流室能够产生2.1 s-1的伸长率，相应的体积平均剪切速率为58.33 s-1。在拉伸应力暴露后，观察到总血小板体积分布和对添加化学拮抗剂的测量反应有显著变化。总血小板体积直方图向较大粒径方向移动，表明由于拉伸应力暴露形成了大聚集体。暴露于拉伸应力的血小板在添加ADP诱导的聚集速率和聚集程度上表现出剂量依赖性降低。
