Rapid changes in the coagulant proteins on saphenous vein endothelium in response to arterial flow

Healthy endothelium provides a nonthrombogenic surface. In this study the a uthors investigated the effect of arterial flow on the saphenous vein endot helial expression of proteins controlling thrombosis. Human saphenous vein segments, freshly excised from patients, were placed in a validated in vitr o circuit with flow conditions shown to simulate arterial or venous circula tions. In separate experiments, placement of an external polytetrafluoroeth ylene (PTFE) stent was used to differentiate the effects of pulsatile wall deformation and shear stress, while addition of drugs to the vein perfusate allowed study of the role of ion channels in transducing the response of t he vein to arterial flow. Endothelial concentrations of thrombomodulin, nit ric oxide synthase, tissue factor, and tissue plasminogen activator were as sessed by quantitative immunohistochemistry and Western blotting of endothe lial cell lysates, in paired vein samples, in comparison to control protein s. Arterial flow conditions caused a rapid and significant reduction in the en dothelial concentration of thrombomodulin: The immunostaining area decrease d from 80.1 +/-7.0 to 48.3 +/-5.0 and 32.9 +/-3.0% at 45 and 90 minutes res pectively, p = 0.01. These findings were confirmed by Western blotting. The reduction in thrombomodulin concentration was unaffected by eliminating ve in wall deformation by placement of an external PTFE stent or by including the K+ channel blocker tetraethylammonium (TEA) in the vein perfusate. In c ontrast, thrombomodulin concentrations remained high when blockers of stret ch-activated cation and calcium-channels were included in the vein perfusat e. The endothelial concentration of nitric oxide synthase increased after 9 0 minutes of arterial flow and this change was abolished when TEA was inclu ded in the vein perfusate. Arterial flow induced rapid changes in saphenous vein antithrombotic proteins. Different cation channels mediated the flow- induced changes in thrombomodulin and nitric oxide synthase.