Joist J H, Cowan J F, Khan M
J Lab Clin Med. 1977 Dec;90(6):1054-65.
Rapid prolongation of the aPTT of normal plasma upon incubation with ellagic acid containing aPTT reagents was observed. The aPTT prolongation was not due to time-dependent changes in pH in the incubation mixture or loss of activity of the labile coagulation factors VIII and V but occurred as a result of rapid progressive inactivation of ellagic acid-activated factors XII and XI. Prolongation of the aPTT and loss of contact factor activities was not observed in plasma incubated with particulate activator reagents. This finding seemed to indicate that adsorption of factors XII and XI to larger particles during the activation process might protect these factors from inactivation by naturally occurring plasma inhibitors. Evidence is presented which supports previous findings that C1-INH, alpha1-AT, and antithrombin (in the presence of heparin) contribute to factor XIIa and XI a inactivation in ellagic acid-activated plasma and that plasma albumin may compete with factor XII for ellagic acid binding. The data indicate that ellagic acid-containing aPTT reagents have unfavorable properties which seriously limit their usefulness in the clinical laboratory, particularly in respect to recording of the aPTT with certain fully automated clot timers.
观察到正常血浆与含鞣花酸的活化部分凝血活酶时间（aPTT）试剂孵育后，aPTT迅速延长。aPTT延长并非由于孵育混合物中pH值的时间依赖性变化或不稳定凝血因子VIII和V活性丧失，而是由于鞣花酸激活的因子XII和XI迅速进行性失活所致。在用颗粒状激活剂试剂孵育的血浆中未观察到aPTT延长和接触因子活性丧失。这一发现似乎表明，在激活过程中因子XII和XI吸附到较大颗粒上可能会保护这些因子不被天然存在的血浆抑制剂灭活。有证据支持先前的发现，即C1-抑制物（C1-INH）、α1-抗胰蛋白酶（alpha1-AT）和抗凝血酶（在肝素存在下）有助于鞣花酸激活的血浆中因子XIIa和XIa的失活，并且血浆白蛋白可能与因子XII竞争鞣花酸结合。数据表明，含鞣花酸的aPTT试剂具有不利特性，严重限制了它们在临床实验室中的实用性，特别是在使用某些全自动凝血计时器记录aPTT方面。
