Simmonds Michael J, Atac Nazli, Baskurt Oguz K, Meiselman Herbert J, Yalcin Ozlem
Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Queensland, Australia.
School of Medicine, Koç University, Sariyer, Istanbul, Turkey.
Biorheology. 2014;51(2-3):171-85. doi: 10.3233/BIR-140665.
Previous studies have demonstrated that red blood cells (RBC) either lyse or at least experience mechanical damage following prolonged exposure to high shear stress (≥100 Pa). Conversely, prolonged shear stress exposure within the physiological range (5-20 Pa, 300 s) was recently reported to improve RBC deformability. This study investigated the relationships between shear stress and RBC deformability to determine the breakpoint between beneficial vs. detrimental exposure to shear stress (i.e., "subhemolytic threshold"). A second aim of the study was to determine whether the frequency of intermittent application of shear stress influenced the subhemolytic threshold.
RBC were exposed to various levels of shear stress (0-100 Pa) in a Couette type shearing system for 300 s. RBC deformability was then immediately measured via ektacytometry. Parallel experiments were conducted at the same shear stresses, except the application time differed while keeping constant the total exposure time: shear stress was applied either for 30 s and repeated 10 times (10×30 s) or applied for 15 s and repeated 20 times (20×15 s).
For a range of donors, the subhemolytic threshold with constant shear stress application was between 30-40 Pa. When physiological shear stress was applied in an intermittent manner, more frequent applications tended to improve (i.e., increase) RBC deformability. However, when supra-physiological shear stress was applied, both continuous and intermittent protocols damaged RBC. Changes of RBC mechanical behavior occurred without increases of hemoglobin in the suspending media, thus attesting to the absence of hemolysis.
Shear stress has a biphasic effect on the mechanical properties of RBC, with the duration and rate of exposure appearing to have minimal impact on the subhemolytic threshold when compared with the magnitude of applied shear stress.
先前的研究表明，长时间暴露于高剪切应力（≥100 Pa）下，红细胞（RBC）会发生裂解或至少遭受机械损伤。相反，最近有报道称，在生理范围内（5 - 20 Pa，300秒）长时间暴露于剪切应力可改善红细胞的变形能力。本研究调查了剪切应力与红细胞变形能力之间的关系，以确定有益与有害的剪切应力暴露之间的断点（即“亚溶血阈值”）。该研究的第二个目的是确定剪切应力间歇施加的频率是否会影响亚溶血阈值。
在库埃特型剪切系统中，将红细胞暴露于不同水平的剪切应力（0 - 100 Pa）下300秒。然后通过激光衍射法立即测量红细胞的变形能力。在相同的剪切应力下进行平行实验，但施加时间不同，同时保持总暴露时间不变：剪切应力施加30秒并重复10次（10×30秒）或施加15秒并重复20次（20×15秒）。
对于一系列供体，持续施加剪切应力时的亚溶血阈值在30 - 40 Pa之间。当以间歇方式施加生理剪切应力时，更频繁的施加往往会改善（即增加）红细胞的变形能力。然而，当施加超生理剪切应力时，连续和间歇方案都会损伤红细胞。红细胞力学行为的变化在悬浮介质中血红蛋白未增加的情况下发生，从而证明没有溶血现象。
剪切应力对红细胞的力学性能具有双相作用，与施加的剪切应力大小相比，暴露的持续时间和速率对亚溶血阈值的影响似乎最小。
