Functional activity of TM (A), HS (B), and TFPI (C). Assays were performed using either adherent (left panels) or suspended cells (right panels). Apoptosis in adherent and suspended HUVECs was induced by treatment with staurosporine (left panels, solid triangles) or culture in suspension with serum deprivation (right panels, shaded triangles) for 8 and 16 hours, respectively. All activities were determined by chromogenic substrate assays as follows: thrombin-dependent activation of protein C (TM activity), ATIII-dependent inhibition of thrombin (HS activity), and inhibition of factor Xa formation generated by the TF-factor VIIa complex (TFPI activity). Controls were untreated cells (all panels; ○). As negative controls (all panels; □), cells were pretreated with LPS (TM), heparinase III (HS), and rabbit antihuman TFPI antibody (TFPI), respectively. Results are expressed as mean ± SD (n = 4).