Nossel H L, Yudelman I, Canfield R E, Butler V P, Spanondis K, Wilner G D, Qureshi G D
J Clin Invest. 1974 Jul;54(1):43-53. doi: 10.1172/JCI107749.
Since thrombin cleaves fibrinopeptides A (FPA) and B from the NH(2)-terminal end of the fibrinogen molecule, measurement of fibrinopeptide levels in plasma may provide a direct index of thrombin action. Recently a radioimmunoassay for FPA has been developed, and in the present paper, we describe the application of this assay to the measurement of FPA levels in clinical blood samples. Since fibrinogen cross-reacts with antibodies to FPA, dialysis was used to extract the peptide from plasma. In vitro generation of FPA was prevented by removing the fibrinogen from the plasma by precipitation with ethanol before dialysis. The processing technique permitted recovery of 75% of FPA added to blood in vitro. Evidence that the immunoreactivity measured in plasma is due to FPA was provided by the results of experiments in which two antisera to FPA with different specificities showed comparable results and addition of thrombin caused no change in immunoreactivity. In contrast, extracts of streptokinasetreated plasma showed a five-fold increase in activity when treated with thrombin and markedly different immunoreactivity with the two antisera. Plasma FPA levels in 30 normal men were below 2 ng/ml, with a mean of 0.5 ng/ml. FPA levels in 12 patients with reduced fibrinogen levels or reduced platelet counts or both ranged between 4 and 289 ng/ml. FPA levels in 13 patients with normal or elevated fibrinogen levels, including 6 patients with clinical evidence of venous thrombosis or pulmonary embolism or both, ranged between 5 and 23 ng/ml. FPA and fibrinogen degradation product levels did not correlate, and in several patients, elevated FPA levels were found in the presence of normal fibrinogen degradation product levels. After infusion of FPA-containing solutions in four normal individuals, FPA showed a disappearance rate from the plasma consistent with a t((1/2)) of 3-5 min. Heparin infusions in six patients with venous thrombosis or pulmonary embolism or both and elevated FPA levels were followed by a prompt decline in FPA level at a mean rate equivalent to a 3-5 min t((1/2)).
由于凝血酶可从纤维蛋白原分子的氨基末端裂解出纤维蛋白肽A（FPA）和B，因此检测血浆中纤维蛋白肽水平可直接反映凝血酶的活性。最近已开发出一种FPA放射免疫测定法，在本文中，我们描述了该测定法在临床血样FPA水平检测中的应用。由于纤维蛋白原与FPA抗体发生交叉反应，因此采用透析法从血浆中提取该肽段。在透析前，通过用乙醇沉淀法去除血浆中的纤维蛋白原，防止了FPA在体外生成。该处理技术可回收体外添加到血液中的75%的FPA。实验结果提供了血浆中测得的免疫反应性归因于FPA的证据，在这些实验中，两种具有不同特异性的FPA抗血清显示出可比的结果，且添加凝血酶后免疫反应性未发生变化。相比之下，链激酶治疗的血浆提取物在用凝血酶处理后活性增加了五倍，并且与两种抗血清的免疫反应性明显不同。30名正常男性的血浆FPA水平低于2 ng/ml，平均为0.5 ng/ml。12名纤维蛋白原水平降低或血小板计数降低或两者均降低的患者的FPA水平在4至289 ng/ml之间。13名纤维蛋白原水平正常或升高的患者，包括6名有静脉血栓形成或肺栓塞或两者临床证据的患者，其FPA水平在5至23 ng/ml之间。FPA和纤维蛋白原降解产物水平不相关，在一些患者中，在纤维蛋白原降解产物水平正常的情况下发现FPA水平升高。在四名正常个体中输注含FPA的溶液后，FPA从血浆中的消失率符合半衰期为3至5分钟的情况。对六名有静脉血栓形成或肺栓塞或两者且FPA水平升高的患者输注肝素后，FPA水平迅速下降，平均下降速率相当于半衰期为3至5分钟。
