Gosling M, Golledge J, Turner R J, Powell J T
Department of Vascular Surgery, Imperial College School of Medicine at Charing Cross, Charing Cross Hospital, London, UK.
Circulation. 1999 Mar 2;99(8):1047-53. doi: 10.1161/01.cir.99.8.1047.
The antithrombogenic properties of venous endothelium may be attenuated when vein is implanted in the arterial circulation. Such changes may facilitate thrombosis, which is the final common pathway for saphenous vein arterial bypass graft occlusion.
Using human saphenous vein in a validated ex vivo flow circuit, we investigated (1) the possibility that arterial flow conditions (mean pressure, 100 mm Hg, 90 cpm, approximately 200 mL/min) alter the concentration of proteins involved in regulating thrombosis at the vessel wall and (2) the influence of ion channel blockade on such effects. Concentrations of thrombomodulin and tissue factor were quantified by Western blotting (ratio of von Willebrand factor staining) and immunohistochemistry (as a percentage of CD31-staining area). Thrombomodulin concentrations after 90 minutes of venous and arterial flow conditions were quantified by immunostaining (68.9+/-4.8% and 41.0+/-3.0% CD31, respectively; P<0.01) and by Western blotting (1.35+/-0.20 and 0. 15+/-0.03 ratio of von Willebrand factor, respectively; P<0.01). The ability of endothelial cells to generate activated protein C also decreased from 62+/-14 to 19+/-10 ng. min-1. 1000 cells-1 (P=0.01). The significant reduction in thrombomodulin was attenuated if calcium was removed from the perfusate but not by external vein stenting. Inclusion in the vein perfusate of drugs that reduce calcium entry (including Gd3+, to block stretch-activated ion channels, and nifedipine) abolished the reduction in thrombomodulin concentration observed after arterial flow conditions. In freshly excised vein, negligible concentrations of tissue factor were detected on the endothelium and concentrations did not increase after 90 minutes of arterial flow conditions, although the inclusion of nifedipine caused the immunostaining to increase from 3.0+/-0.4% to 8.5+/-0.7% CD31 (P<0.02).
In saphenous vein endothelium exposed to arterial flow conditions, there is rapid downregulation of thrombomodulin, sufficient to limit protein C activation, by a calcium-dependent mechanism.
当静脉植入动脉循环时，静脉内皮的抗血栓形成特性可能会减弱。这种变化可能会促进血栓形成，而血栓形成是大隐静脉动脉搭桥移植物闭塞的最终共同途径。
在经过验证的体外血流回路中使用人隐静脉，我们研究了：（1）动脉血流条件（平均压力100mmHg，90次/分钟，约200mL/分钟）改变血管壁上参与调节血栓形成的蛋白质浓度的可能性；（2）离子通道阻滞剂对这种作用的影响。通过蛋白质印迹法（血管性血友病因子染色比率）和免疫组织化学法（作为CD31染色面积的百分比）对血栓调节蛋白和组织因子的浓度进行定量。通过免疫染色（分别为68.9±4.8%和41.0±3.0%的CD31；P<0.01）和蛋白质印迹法（血管性血友病因子的比率分别为1.35±0.20和0.15±0.03；P<0.01）对静脉和动脉血流条件90分钟后的血栓调节蛋白浓度进行定量测定。内皮细胞产生活化蛋白C的能力也从62±14降至19±10ng·min-1·1000细胞-1（P=0.01）。如果从灌注液中去除钙，血栓调节蛋白的显著降低会减弱，但外部静脉支架置入则不会。在静脉灌注液中加入减少钙内流的药物（包括钆离子，以阻断牵张激活离子通道，以及硝苯地平）可消除动脉血流条件后观察到的血栓调节蛋白浓度降低。在新鲜切除的静脉中，在内皮上检测到的组织因子浓度可忽略不计，并且在动脉血流条件90分钟后浓度没有增加，尽管加入硝苯地平导致免疫染色从3.0±0.4%增加到8.5±0.7%的CD31（P<0.02）。
在暴露于动脉血流条件的隐静脉内皮中，血栓调节蛋白通过钙依赖机制迅速下调，足以限制蛋白C的激活。
