Ruf A, Patscheke H
Institute for Medical Laboratory Diagnostics, Klinikum Karlsruhe, Germany.
Semin Thromb Hemost. 1995;21(2):146-51. doi: 10.1055/s-2007-1000389.
Platelet activation plays an important role in the pathomechanisms of arterial vascular disorders including stroke, peripheral arterial disease (PAD), and myocardial infarction. Circulating activated platelets may be useful markers of local thrombotic events occurring in these diseases. Using flow cytometry circulating activated platelets can be detected by determining: 1. the platelets' shape change on the basis of the different light scatter properties of discocytes and spherocytes, 2. the expression of platelet bound fibrinogen or conformation specific neoantigens on fibrinogen and on its platelet receptor, and 3. the exposure of granule membrane proteins such as P-selectin as a result of platelet secretion. The concentration-effect relationships were determined for the ADP and U46619 induced shape change, fibrinogen binding, and expression of P-selectin. The EC50 for the shape change was 4 times lower than the EC50 for the fibrinogen binding and 29 times lower than the EC50 for the expression of P-selectin. These data clearly demonstrate that the shape change is a more sensitive indicator of platelet activation in vitro than fibrinogen binding or P-selectin expression. Both the shape change and fibrinogen binding were reversible, whereas the expression of P-selectin was irreversible upon stimulation. Reversibility of the shape change may be responsible for the fact that in patients with stroke or PAD the fraction of discocytes did not differ from controls, whereas more than 80% of them revealed a significantly higher fraction of P-selectin positive platelets. Thus the determination of the P-selectin expression reveals a higher diagnostic sensitivity for detecting a platelet activation in vivo than the determination of the shape change.
血小板活化在包括中风、外周动脉疾病（PAD）和心肌梗死在内的动脉血管疾病的发病机制中起着重要作用。循环中的活化血小板可能是这些疾病中发生的局部血栓形成事件的有用标志物。使用流式细胞术，可通过以下方式检测循环中的活化血小板：1. 根据圆盘状血小板和球形血小板不同的光散射特性来确定血小板的形状变化；2. 检测血小板结合纤维蛋白原或纤维蛋白原及其血小板受体上构象特异性新抗原的表达；3. 检测由于血小板分泌导致的颗粒膜蛋白如P-选择素的暴露。测定了ADP和U46619诱导的形状变化、纤维蛋白原结合以及P-选择素表达的浓度-效应关系。形状变化的半数有效浓度（EC50）比纤维蛋白原结合的EC50低4倍，比P-选择素表达的EC50低29倍。这些数据清楚地表明，在体外，形状变化比纤维蛋白原结合或P-选择素表达更敏感地指示血小板活化。形状变化和纤维蛋白原结合都是可逆的，而刺激后P-选择素的表达是不可逆的。形状变化的可逆性可能是导致中风或PAD患者中圆盘状血小板的比例与对照组无差异，而其中超过80%的患者显示P-选择素阳性血小板比例显著更高的原因。因此，与测定形状变化相比，测定P-选择素表达在检测体内血小板活化方面具有更高的诊断敏感性。
