Vanschoonbeek K, Feijge M A H, Van Kampen R J W, Kenis H, Hemker H C, Giesen P L A, Heemskerk J W M
Department of Human Biology, Cardiovascular Research Institute of Maastricht, The Netherlands.
J Thromb Haemost. 2004 Mar;2(3):476-84. doi: 10.1111/j.1538-7933.2004.00618.x.
The hemostatic activity of plasma is determined by platelet activation and coagulation, which processes are mutually stimulatory. We studied this interaction by measuring the cleavage of fluorescent thrombin substrate in platelet-rich plasma (PRP), using the calibrated thrombogram method. In freshly isolated human plasma, thrombin formation triggered by tissue factor was fully dependent on the presence of platelets. It was abolished by annexin A5, indicating dependence on phosphatidylserine (PS) exposure at activated platelets. Comparison of plasmas from various subjects showed considerable interindividual variation in total amount of thrombin generation, regardless of whether platelets or PS-containing phospholipids were present. Integrin alphaIIbbeta3 antagonists and ADP receptor blockage, but not aspirin, decreased the rate of thrombin generation (thrombin peak level) and extended the time of onset. Platelet inhibition with cAMP-elevating agents decreased the thrombin-forming rate, but surprisingly shortened the onset time. Stimulation of platelets with agonists of Gi/q-coupled receptors and, to a larger extent, with collagen or Ca2+-ionophore increased the rate of thrombin generation and shortened its onset. In PRP from donors with low and high generation, platelet inhibitors and activators were similarly effective. Taken together, these results indicate that, in tissue factor-triggered PRP, PS exposure on activated platelets regulates both onset and rate of thrombin generation. However, coagulant activity rather than platelet activation determines the total amount of thrombin formed, i.e. the endogenous thrombin potential. Thus, kinetics of thrombin generation in PRP are controlled by platelet inhibitors and agonists, but the process is restricted in amount by the subject-dependent variation in coagulation.
血浆的止血活性由血小板活化和凝血决定，这两个过程相互刺激。我们使用校准血栓图法，通过测量富血小板血浆（PRP）中荧光凝血酶底物的裂解来研究这种相互作用。在新鲜分离的人血浆中，组织因子触发的凝血酶形成完全依赖于血小板的存在。它被膜联蛋白A5消除，表明依赖于活化血小板上磷脂酰丝氨酸（PS）的暴露。对来自不同受试者的血浆进行比较显示，无论是否存在血小板或含PS的磷脂，凝血酶生成总量存在相当大的个体间差异。整合素αIIbβ3拮抗剂和ADP受体阻断剂，但不是阿司匹林，降低了凝血酶生成速率（凝血酶峰值水平）并延长了起效时间。用升高cAMP的药物抑制血小板降低了凝血酶形成速率，但令人惊讶的是缩短了起效时间。用Gi/q偶联受体激动剂刺激血小板，以及在更大程度上用胶原蛋白或Ca2+离子载体刺激血小板，增加了凝血酶生成速率并缩短了其起效时间。在凝血酶生成低和高的供体的PRP中，血小板抑制剂和激活剂同样有效。综上所述，这些结果表明，在组织因子触发的PRP中，活化血小板上的PS暴露调节凝血酶生成的起效和速率。然而，凝血活性而非血小板活化决定了形成的凝血酶总量，即内源性凝血酶潜力。因此，PRP中凝血酶生成的动力学受血小板抑制剂和激动剂控制，但该过程在量上受到受试者凝血相关个体差异的限制。
