FVIII storage and release by ECs. Endothelial cells (A, HCMECs; B, HDMECs; C, HIMECs, and D, HAECs) were plated in microculture wells and kept 8 days in culture. After washing, the cells were incubated in culture medium supplemented with 100nM PMA or epinephrine (epi) at 100 and 10 ng/mL. FVIII concentrations (left y-axis; ●) and VWF:Ag (right y-axis; ○) were measured in culture supernatant collected 1 hour after the addition of the medium. Results are expressed in logarithmic scale as FVIII and VWF concentration in individual microculture wells. **P < .001; *P < .05