Decreased expression and activity of TF in Gas6^−/− endothelial cells. (A) In vitro, low TF activity was also found in the media of Gas6^−/− endothelial cells compared with WT cells (n = 6-8). *P < .05. (B) Quantitative PCR showed that TF mRNA expression was low in Gas6^−/− deficient endothelial cells compared with WT. Thrombin treatment increased significantly TF mRNA expression in WT but not in Gas6^−/− cells. When Gas6^−/− cells were treated with both thrombin and murine recombinant Gas6, TF mRNA expression was increased to a level comparable with WT cells. Murine recombinant Gas6 alone has no significant effect on TF mRNA expression in WT or Gas6^−/− cells (n = 4-10). *P < .05 vs Gas6^−/− untreated cells. #P < .05 vs untreated WT cells. (C) Thrombin induced Gas6 mRNA in WT endothelial cells (n = 4-8). *P < .05.