Hu Hu, Forslund Mikael, Li Nailin
Department of Medicine, Clinical Pharmacology Unit, Karolinska University Hospital-Solna, SE-171 76 Stockholm, Sweden.
Thromb Res. 2005;116(3):241-7. doi: 10.1016/j.thromres.2004.12.015. Epub 2005 Jan 18.
The influence of extracellular calcium concentrations ([Ca(2+)]) on single platelet activation and platelet aggregation was evaluated. Platelet fibrinogen binding and P-selectin expression were monitored by whole blood flow cytometry in the presence of EDTA or 0.125, 1.25, 2.5, 5, or 10 mM [Ca(2+)] and in the absence or presence of the thromboxane A(2) (TXA(2)) blockade. Platelet aggregation was measured in citrated and hirudinized platelet-rich plasma (PRP). Platelet fibrinogen binding was slightly increased at >/=2.5 mM [Ca(2+)] in unstimulated samples. ADP-induced platelet fibrinogen binding was, however, higher at 0.125 mM, but lower at 5 and 10 mM [Ca(2+)], as compared to 1.25 mM [Ca(2+)]. Platelet P-selectin expression was not affected by extracellular [Ca(2+)], except mild increases of ADP-induced platelet P-selectin expression in the presence of EDTA. TXA(2) blockade by ICI 192.605 influenced above flow cytometric analyses little. Using Born aggregometry, ADP induced more intense platelet aggregation in citrated PRP than in hirudinized PRP. TXA(2) blockade did not affect platelet aggregation in hirudinized PRP, but reduced aggregation in citrated PRP to approximately 85% of that in hirudinized samples. ADP also induced a more marked and sustained elevation of intracellar [Ca(2+)] in the presence of extracellular [Ca(2+)]. Thus, extracellular [Ca(2+)] has little influence on flow cytometric analysis of platelet P-selectin expression. High [Ca(2+)] enhances spontaneous platelet fibrinogen binding, but reduces ADP-induced platelet fibrinogen binding, while low [Ca(2+)] enhances ADP-induced platelet fibrinogen binding. Physiological [Ca(2+)] supports more intense platelet aggregation when effect of artificial TXA(2) synthesis is blocked.
评估了细胞外钙浓度（[Ca(2+)]）对单个血小板活化和血小板聚集的影响。在存在乙二胺四乙酸（EDTA）或0.125、1.25、2.5、5或10 mM [Ca(2+)]以及存在或不存在血栓素A2（TXA2）阻断的情况下，通过全血流式细胞术监测血小板纤维蛋白原结合和P-选择素表达。在枸橼酸化和水蛭素化的富血小板血浆（PRP）中测量血小板聚集。在未刺激的样本中，当[Ca(2+)]≥2.5 mM时，血小板纤维蛋白原结合略有增加。然而，与1.25 mM [Ca(2+)]相比，ADP诱导的血小板纤维蛋白原结合在0.125 mM时更高，但在5和10 mM [Ca(2+)]时更低。血小板P-选择素表达不受细胞外[Ca(2+)]的影响，除了在存在EDTA的情况下，ADP诱导的血小板P-选择素表达略有增加。ICI 192.605对TXA2的阻断对上述流式细胞术分析影响很小。使用Born凝集测定法，ADP在枸橼酸化PRP中比在水蛭素化PRP中诱导更强烈的血小板聚集。TXA2阻断不影响水蛭素化PRP中的血小板聚集，但将枸橼酸化PRP中的聚集降低至水蛭素化样本中的约85%。在存在细胞外[Ca(2+)]的情况下，ADP还诱导细胞内[Ca(2+)]更显著和持续的升高。因此，细胞外[Ca(2+)]对血小板P-选择素表达的流式细胞术分析影响很小。高[Ca(2+)]增强自发性血小板纤维蛋白原结合，但降低ADP诱导的血小板纤维蛋白原结合，而低[Ca(2+)]增强ADP诱导的血小板纤维蛋白原结合。当人工TXA2合成的作用被阻断时，生理[Ca(2+)]支持更强烈的血小板聚集。
