Sanchez J, Elgue G, Larsson R, Nilsson B, Olsson P
Department of Radiology, Oncology and Clinical Immunology, Division of Clinical Immunology, The Rudbeck Laboratory, University Hospital, Uppsala, Sweden.
Thromb Res. 2008;122(2):257-63. doi: 10.1016/j.thromres.2007.11.008. Epub 2008 Feb 21.
This study was designed to investigate whether fibrinogen, soluble desAA-fibrin, and insoluble desAABB-fibrin are able to induce clotting by triggering the plasma contact activation system when adsorbed to polystyrene.
The above-mentioned substances were individually prepared on polystyrene meshwork squares, and then exposed to a purified FXII solution or non-calcium containing plasma (citrated and dialyzed normal pooled plasma) in polystyrene cuvettes coated with surface-immobilized heparin, to completely block contact activation and the coagulation mechanism that might be induced by the cuvette surfaces. Sodium glass beads were used as the reference material.
On exposure to purified FXII solution and plasma, all the tested materials adsorbed and activated FXII to varying degrees. This activation led to the formation of FXIa in the exposed plasma, with the highest activation occurring upon exposure to glass, desAA-fibrin and desAABB-fibrin and the lowest upon exposure to fibrinogen-adsorbed or unmodified polystyrene meshwork squares. Following recalcification, in cuvettes with surface-immobilized heparin, a spectrophotometric assay showed that the surface-exposed plasma aliquots clotted within 5 min after contact with glass, within 10 to 15 min after contact with the two forms of fibrin, and somewhat longer after contact with adsorbed fibrinogen. The longest lag phase, close to 20 min, occurred in plasma exposed to unmodified polystyrene meshwork. Whole blood deposited in surface heparinized cuvettes directly from the cubital vein did not clot during the observation time (2 h).
These results indicate that domains induced by conformational changes in adsorbed fibrinogen and fibrin are capable of activating adsorbed proenzymes and that various forms of fibrin are considerably stronger activators of the contact activation system than are adsorbed fibrinogen or a polystyrene meshwork. The delayed coagulation in plasma exposed to the unmodified polystyrene meshwork can be explained by a two-step process: first, adsorption of fibrinogen, and second, activation of FXII. Under our experimental conditions, the adsorption and activation of FXII on fibrinogen and fibrin seems to be an important mechanism for triggering coagulation.
本研究旨在调查纤维蛋白原、可溶性去氨基末端 A 纤维蛋白和不溶性去氨基末端 AABB 纤维蛋白吸附到聚苯乙烯上时，是否能够通过触发血浆接触激活系统来诱导凝血。
上述物质分别制备在聚苯乙烯网片方块上，然后置于涂有表面固定化肝素的聚苯乙烯比色皿中，暴露于纯化的 FXII 溶液或不含钙的血浆（枸橼酸化并透析的正常混合血浆）中，以完全阻断接触激活以及比色皿表面可能诱导的凝血机制。钠玻璃珠用作参考材料。
暴露于纯化的 FXII 溶液和血浆后，所有测试材料均不同程度地吸附并激活了 FXII。这种激活导致暴露血浆中形成 FXIa，暴露于玻璃、去氨基末端 A 纤维蛋白和去氨基末端 AABB 纤维蛋白时激活程度最高，而暴露于吸附纤维蛋白原或未修饰的聚苯乙烯网片方块时激活程度最低。重新添加钙离子后，在表面固定化肝素的比色皿中，分光光度法测定显示，表面暴露的血浆等分试样在与玻璃接触后 5 分钟内凝结，与两种形式的纤维蛋白接触后 10 至 15 分钟内凝结，与吸附的纤维蛋白原接触后凝结时间稍长。暴露于未修饰聚苯乙烯网片的血浆中出现最长的延迟期，接近 20 分钟。直接从肘静脉采集并置于表面肝素化比色皿中的全血在观察时间（2 小时）内未凝结。
这些结果表明，吸附的纤维蛋白原和纤维蛋白构象变化诱导的结构域能够激活吸附的酶原，并且各种形式的纤维蛋白对比色皿表面可能诱导的凝血机制。吸附的纤维蛋白原或聚苯乙烯网片是接触激活系统更强的激活剂。暴露于未修饰聚苯乙烯网片的血浆中凝血延迟可通过两步过程来解释：首先是纤维蛋白原的吸附，其次是 FXII 的激活。在我们的实验条件下，FXII 在纤维蛋白原和纤维蛋白上的吸附和激活似乎是触发凝血的重要机制。
