Quantification of ADAMTS13 and VWF secreted by unstimulated and histamine-stimulated HUVECs. Culture media was collected from HUVECs grown in 48-well plates at 0, 5, 15, 30, 60, and 180 minutes after the addition of 60 μL of serum-free media with 1% BSA ± 100μM histamine. Samples were collected into 10mM EDTA, and levels of VWF and ADAMTS-13 were measured by immunoassay. (A) There were no significant differences in the ADAMTS-13 levels (pg/mL) measured from the stimulated (•) and unstimulated HUVECs (■) at each time point (n = 8-10). (B) Levels of VWF secreted after histamine stimulation (■) and VWF released in the absence of stimulation (•) were significantly different at each point measured after 0 minutes (n = 5-6).