StxB-induced VWF secretion requires cholesterol but not clathrin. (A) HUVECs were incubated without (0) or with 10 mg/mL methyl-β-cyclodextrin (Mβ) or α-cyclodextrin (α) for 15 minutes at 37°C before perfusion with Stx1B or Stx2B (200 ng/mL; A) or histamine (100μM; B) and quantification of VWF strings. (C) HUVECs were preincubated without or with 1 μg/mL filipin (Fil) or 5 μg/mL chlorpromazine (Cpz) for 1 hour at 37°C, or with hypertonic medium containing 0.45M sucrose (Hyp) for 30 minutes at 37°C, perfused with Stx1B or Stx2B (200 ng/mL), and VWF strings were quantified. These experiments were conducted 3 times with similar results. Values are shown as mean ± SE.