StxB-induced VWF secretion is reduced upon caveolin-1 knockdown. HUVECs were transfected with siRNA for caveolin-1 (Cav1), or green fluorescent protein (Ctrl). At 72 hours, (A) caveolin-1 (Cav1) and β-actin (β-Act) were detected in cell lysates by Western blotting with monoclonal anti–caveolin-1 (BD Biosciences) or anti–β-actin (AC-15; Sigma-Aldrich), normalizing band densities for Cav1 to β-actin for comparison to the mock condition (100%); or (B) the cells were treated under static conditions with histamine (100μM), Stx1B or Stx2B (200 ng/mL) and secreted cell-surface VWF assayed by cell-surface ELISA; or (C) cells were perfused with Stx1B or Stx2B and VWF strings were quantified. Indicated comparisons between Ctrl and Cav1 siRNA are significant at P < .05 (*) or P < .01 (**) by Student t test. These experiments were performed at least 3 times with similar results. Values are shown as mean ± SE.