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

Abstract

Healthy endothelium provides a nonthrombogenic surface. In this study the authors investigated the effect of arterial flow on the saphenous vein endothelial expression of proteins controlling thrombosis. Human saphenous vein segments, freshly excised from patients, were placed in a validated in vitro circuit with flow conditions shown to simulate arterial or venous circulations. In separate experiments, placement of an external polytetrafluoroethylene (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 the vein to arterial flow. Endothelial concentrations of thrombomodulin, nitric oxide synthase, tissue factor, and tissue plasminogen activator were assessed by quantitative immunohistochemistry and Western blotting of endothelial cell lysates, in paired vein samples, in comparison to control proteins. Arterial flow conditions caused a rapid and significant reduction in the endothelial concentration of thrombomodulin: The immunostaining area decreased from 80.1 +/- 7.0 to 48.3 +/- 5.0 and 32.9 +/- 3.0% at 45 and 90 minutes respectively, p = 0.01. These findings were confirmed by Western blotting. The reduction in thrombomodulin concentration was unaffected by eliminating vein wall deformation by placement of an external PTFE stent or by including the K+ channel blocker tetraethylammonium (TEA) in the vein perfusate. In contrast, thrombomodulin concentrations remained high when blockers of stretch-activated cation and calcium channels were included in the vein perfusate. The endothelial concentration of nitric oxide synthase increased after 90 minutes of arterial flow and this change was abolished when TEA was included 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.