Multimeric states of endothelial cell VWF secreted from 3 different pathways. (A) Representative multimer pattern of secreted VWF collected for 30 minutes from unstimulated HUVECs, treated with 5 μM of Brefeldin A (+BFA) for 1 hour before and during secretion collection, treated with 100 μM histamine or 100 ng/mL of PMA. VWF ELISA was used to measure the amount of VWF secreted in all conditions and the same units of VWF were loaded on an SDS/agarose gel (migrations shown from top to bottom). A parallel sample of human plasma is shown for comparison (Plasma VWF). Relative VWF amount ratios in this experiment are 1:1:5:16 = constitutive:basal:histamine:PMA. (B) Representative line plots from the multimer patterns shown in (A). A.U., arbitrary units. (C) Diagram of multimer patterns of plasma VWF and VWF secreted via the constitutive, basal, and regulated secretory pathways from endothelial cells. UL, ultralarge; HMW, high-molecular-weight; LMW, low-molecular-weight.