APC pretreatment reduces thrombin-mediated hyperpermeability. (A) Confluent EA.hy926 cells were incubated for the indicated periods with 20 nM APC followed by a 10-minute incubation with thrombin. Permeability was tested after 10 minutes (•) and 20 minutes (○) (mean ± SD, n = 3, *P < .05 and **P < .005 compared to no APC). (B) Confluent cells were incubated for 3 hours with the indicated concentrations of APC followed by a 10-minute incubation with thrombin. (•) and (○) represent results from 2 of 4 independent experiments. (C) In parallel experiments confluent cells were either incubated for 3 hours with the indicated concentrations of APC followed by a 10-minute incubation with thrombin (•) or for 3 hours with medium control followed by a 10-minute incubation with the indicated concentrations of APC (○) (mean ± SD, n = 4, *P < .05 and **P < .005 compared to no APC).