Time course of ATP-induced vWF release. Confluent HUVECs grown in 24-well plates were incubated for the indicated times with 100 μmol/L ATP, ATP/IBMX (both 100 μmol/L, ATP/I), 1 U/mL thrombin (Thr), or 1 U/mL thrombin and 100 μmol/L IBMX (Thr/I). Control cells were incubated with KRBH-BSA 0.1% alone (Contr) or supplemented with 100 μmol/L IBMX (I). Results are the mean ± SEM of 5 experiments; error bars were omitted for the sake of clarity. The SEMs were less than 25% of the mean of all values.