Activation of PAR1 or PAR2 increases tissue factor expression at the cell surface. Fibroblasts were incubated with a control buffer or a buffer containing different PAR agonist peptides (50 μM) for 2 hours at 37°C. The cell surface TF expression was evaluated in a TF functional activity assay (in factor X activation assay) (A), TF-specific ¹²⁵I-FVIIa binding (C), and ¹²⁵I-TF mAB binding (D) assays. Panel B depicts cell surface prothrombinase activity in control fibroblasts and fibroblasts treated with different agonist peptides as in panel A. * denotes that the value significantly differs from the value obtained with fibroblasts treated with a control vehicle (n = 3, mean ± SEM).