Thrombin-induced PDI and VWF release from HUVECs treated with HPS6 siRNA. Thrombin-induced PDI release and VWF release from HUVECs 72 hours posttransfection with HPS6 or control siRNA were detected by SDS-PAGE, followed by immunoblotting with anti-PDI antibodies (DL-11; 1 μg/mL) and anti-VWF antibodies (rabbit polyclonal; 1 μg/mL), respectively. Band densities of released PDI from HUVECs (A) or VWF released from HUVECs (B) over 30 minutes after thrombin stimulation (1 NIH U/mL) 72 hours posttransfection with control siRNA (closed bars) or HPS6 siRNA (open bars). Control is shown as 100%. Data represent mean ± SD (n = 3; ***P < .001, **P < .01). (C) When eptifibatide (10 μg/g mouse) was infused, platelet accumulation was prevented in WT mice (black) and in HPS6^−/− mice (gray). (D) Eptifibatide did not blunt the median integrated PDI fluorescence intensity during thrombus formation in WT mice (black) but did so in HPS6^−/− mice (gray). These results are consistent with defective PDI release from the endothelium in HPS6^−/− mice. Data in panels C and D are from 30 thrombi in 3 mice for HPS6^−/− and for WT mice.