Gerotziafas G T, Bara L, Bloch M F, Makris P E, Samama M M
Service d'Hématologie Biologique, Hôpital Hôtel-Dieu, Paris, France.
Blood Coagul Fibrinolysis. 1998 Oct;9(7):571-80. doi: 10.1097/00001721-199810000-00002.
We studied the effect of synthetic pentasaccharide, a low-molecular-weight heparin (enoxaparin), unfractionated heparin and recombinant hirudin on the generation of factor VIIa (FVIIa) and prothrombin activation after in-vitro clotting of human platelet-poor plasma. FVIIa was measured with a new clotting assay that uses recombinant tissue factor truncated to interact only with FVIIa. Residual prothrombin was measured using the conventional clotting assay. FVIIa and residual FII were measured in the liquid - called pseudo-serum (psi-serum) - obtained 1 h after clotting of normal platelet-poor plasma. A kinetic study of the generation of FVIIa was also performed. Coagulation was initiated by triggering the extrinsic, the intrinsic and both associated clotting pathways. Levels of FVIIa in the psi-sera (55+/-15, 258+/-18, and 164+/-18 ng/ml, in the extrinsic, intrinsic and intrinsic + thromboplastin psi-serum respectively; values are means+/-SEM) were significantly increased compared with those in the platelet-poor plasma (3 ng/ml). Pentasaccharide, low-molecular-weight heparin and unfractionated heparin inhibited the generation of factor VIIa or its activity, or both, in a dose-dependent manner in all the experimental systems (60-90% inhibition). A kinetic study revealed that the inhibition of the generation of FVIIa by pentasaccharide and heparins starts 1 min after triggering either the extrinsic or the intrinsic clotting pathway. The downregulation of FVIIa by heparins was effected mainly by their anti-Xa activity, but also by their inhibitory effect on the generation of prothrombinase. Pentasaccharide, enoxaparin and unfractionated heparin significantly inhibited prothrombin activation in both extrinsic and intrinsic experimental system. Hirudin had no inhibitory effect either on the generation of FVIIa or on prothrombin activation in any experimental system.
我们研究了合成五糖、低分子量肝素（依诺肝素）、普通肝素和重组水蛭素对人乏血小板血浆体外凝血后因子VIIa（FVIIa）生成及凝血酶原激活的影响。采用一种新的凝血测定法测量FVIIa，该方法使用截短的重组组织因子，使其仅与FVIIa相互作用。使用传统凝血测定法测量残余凝血酶原。在正常乏血小板血浆凝血1小时后获得的液体（称为假血清，psi-血清）中测量FVIIa和残余FII。还进行了FVIIa生成的动力学研究。通过触发外源性、内源性及两者相关的凝血途径启动凝血。与乏血小板血浆（3 ng/ml）相比，psi-血清中FVIIa水平（外源性、内源性和内源性+凝血活酶psi-血清中分别为55±15、258±18和164±18 ng/ml；数值为平均值±标准误）显著升高。在所有实验系统中，五糖、低分子量肝素和普通肝素均以剂量依赖性方式抑制因子VIIa的生成或其活性，或两者均抑制（抑制率为60 - 90%）。动力学研究表明，五糖和肝素对FVIIa生成的抑制在触发外源性或内源性凝血途径1分钟后开始。肝素对FVIIa的下调主要通过其抗Xa活性，但也通过其对凝血酶原酶生成的抑制作用。五糖、依诺肝素和普通肝素在体外源性和内源性实验系统中均显著抑制凝血酶原激活。在任何实验系统中，水蛭素对FVIIa生成或凝血酶原激活均无抑制作用。
