Aarts P A, van den Broek S A, Prins G W, Kuiken G D, Sixma J J, Heethaar R M
Department of Hematology, University Hospital Utrecht, The Netherlands.
Arteriosclerosis. 1988 Nov-Dec;8(6):819-24. doi: 10.1161/01.atv.8.6.819.
Hematocrit and vessel wall shear rate are important factors in the transport and subsequent adherence of platelets to vessel wall subendothelium. When mass transport theory is applied to platelets in flowing blood, the blood is usually considered to be a fluid with platelet and red cell wall concentrations similar to the average tube concentration. With the laser-Doppler technique, we found how red blood cell ghosts and platelets were distributed radially for various hematocrits and wall shear rates. Red cell ghosts are crowded near the axis of the tube, with a local hematocrit higher than the average tube hematocrit, and they decrease steadily toward the wall. In the absence of ghosts, platelets exhibit the 'tubular pinch' effect (rigid particles crowding at 0.6 x tube radius). In the presence of ghosts, the platelets are expelled toward the wall region. This high concentration at the wall increases with higher average tube hematocrit and wall shear rates. Increasing the average tube platelet concentration 10 times causes the wall concentration to increase only three times. The increase in platelet adherence observed with increasing hematocrit and increasing wall shear rate can be partially ascribed to increased platelet concentration near the wall. The observation that the increased platelet concentration does not fully explain the platelet adherence data suggests that platelet transport may also be enhanced by a shear rate-dependent rotary motion.
血细胞比容和血管壁剪切速率是血小板向血管壁内皮下层运输并随后黏附的重要因素。当将质量传输理论应用于流动血液中的血小板时，血液通常被视为一种流体，其血小板和红细胞壁浓度与平均管内浓度相似。通过激光多普勒技术，我们发现了在不同血细胞比容和壁剪切速率下，红细胞影和血小板在管内的径向分布情况。红细胞影聚集在管轴附近，局部血细胞比容高于平均管内血细胞比容，并且它们朝着管壁稳定减少。在没有红细胞影的情况下，血小板表现出“管状挤压”效应（刚性颗粒聚集在0.6倍管半径处）。在有红细胞影的情况下，血小板被驱向管壁区域。随着平均管内血细胞比容和壁剪切速率的增加，管壁处的这种高浓度会增加。将平均管内血小板浓度增加10倍只会使管壁浓度增加3倍。随着血细胞比容增加和壁剪切速率增加而观察到的血小板黏附增加，部分可归因于管壁附近血小板浓度的增加。血小板浓度增加并不能完全解释血小板黏附数据这一观察结果表明，血小板运输也可能通过与剪切速率相关的旋转运动而增强。
