Bennett J S, Vilaire G
J Clin Invest. 1979 Nov;64(5):1393-401. doi: 10.1172/JCI109597.
The role of fibrinogen as a cofactor for platelet aggregation was examined by measuring the binding of 125I-labeled human fibrinogen to gel-filtered human platelets both before and after platelet stimulation by ADP and epinephrine. Platelet stimulation by ADP resulted in the rapid, reversible binding of fibrinogen to receptors on the platelet surface. Fibrinogen binding increased as the concentration of ADP was increased from 0.1 to 2 microM, reaching a plateau at higher ADP concentrations. Binding occurred only after platelet stimulation and in the presence of divalent cations. However, fibrinogen binding did not occur to ADP-stimulated platelets from three patients with Glanzmann's thrombasthenia. Analysis of fibrinogen binding as a function of increasing fibrinogen concentration demonstrated that maximal platelet stimulation exposed approximately or equal to 45,000 binding sites per platelet with a dissociation constant of 80--170 nM. These fibrinogen binding parameters were essentially the same whether ADP or epinephrine was the platelet-stimulating agent. Thus, these studies demonstrate that platelet stimulation by ADP and epinephrine exposes a limited number of fibrinogen receptors on the platelet surface. Furthermore, these data suggest that the fibrinogen molecules bound to the platelet as a consequence of platelet stimulation are directly involved in the platelet aggregation response.
通过测量在ADP和肾上腺素刺激人血小板前后，125I标记的人纤维蛋白原与凝胶过滤后的人血小板的结合情况，研究了纤维蛋白原作为血小板聚集辅因子的作用。ADP刺激血小板导致纤维蛋白原快速、可逆地结合到血小板表面的受体上。随着ADP浓度从0.1微摩尔增加到2微摩尔，纤维蛋白原结合增加，在更高的ADP浓度下达到平台期。结合仅在血小板刺激后且存在二价阳离子的情况下发生。然而，来自三名Glanzmann血小板无力症患者的ADP刺激血小板未发生纤维蛋白原结合。分析纤维蛋白原结合量随纤维蛋白原浓度增加的变化情况表明，最大程度的血小板刺激使每个血小板暴露约45,000个结合位点，解离常数为80 - 170纳摩尔。无论ADP还是肾上腺素作为血小板刺激剂，这些纤维蛋白原结合参数基本相同。因此，这些研究表明，ADP和肾上腺素刺激血小板会在血小板表面暴露有限数量的纤维蛋白原受体。此外，这些数据表明，由于血小板刺激而结合到血小板上的纤维蛋白原分子直接参与血小板聚集反应。
