Abstract 853

Most in vitro studies of endothelial cell function are still performed using human umbilical vein endothelial cells (HUVECs), with infrequent regard to the tissue source (conceptus vs adult) or to the arterial, microvascular, vs venous origin of the cells. We have therefore undertaken a study of HUVECs vs adult saphenous vein endothelial cells (HSVECs) with regard to the tissue factor pathway of coagulation. We employed a chromogenic assay for production of factor Xa (functional tissue factor (TF)), an ELISA for supernatant tissue factor pathway inhibitor (TFPI), and northern blots for TF mRNA. In response to 50 U/ml × 4 hrs of IL-1-alpha, we found that low-passage HUVECs under static conditions produce 6.50+/- 1.01 (N=10) fmol factor Xa/min per 100,000 endothelial cells, vs 2.70 (6) for low-passage HSVECs (P<0.01). At the same time, levels of supernatant TFPI (in equilibrium with cell-associated TFPI) and TF mRNA were similar. The apparent association constants of TFPI with the endothelial cells were also similar, as assessed by measurements of factor Xa production in the presence of varying concentrations of an anti-TFPI monoclonal antibody. Qualitatively like factor Xa generation was seen following TNF-alpha. Following exposure to shear stress × 4 hrs, HUVECs activated with IL-1-alpha generated less factor Xa: 3.59 +/- 1.49 (N=5) at 0.27 dynes/cm2 and 0.45 +/- 0.45 (3) at 13.2 dynes/cm2. Parallel studies with HSVECs are in progress. We conclude that HUVECs and HSVECs, while responsive to cytokine activation and modulation of this activation under flow conditions, are not equivalent in terms of the tissue factor pathway of coagulation and, indeed, are unlikely to be equivalent models for endothelial cell function in small children vs adults.