Inhibitors of Stx-induced Ca²⁺ responses and VWF secretion. (A-B) Changes in intracellular Ca²⁺ concentration were measured in 96-well plates with a BD calcium assay kit. Fluorescence signals were recorded for 6 wells per condition at 10-second intervals, and the means are plotted; SE values are < 2% of the means. Each experiment repeated at least 3 times with similar results. (A) HUVECs were treated without (Control) or with 1 U/mL thrombin, 5nM Stx1, 5nM Stx1B, 5nM Stx2, or 5nM Stx2B. (B) HUVECs were stimulated with 5nM Stx1B after pretreatment as indicated with 50nM staurosporine (Stauro), 5μM U73122, 5μM H89, or 100μM BAPTA-AM. (C) HUVECs were stimulated without (Control) or with 5nM Stx1B (closed bars) or 5nM Stx2B (open bars) after pretreatment with 100μM BAPTA-AM, Ca²⁺-free medium, 5μM U73122, or 19-31 amide. All comparisons between treatment with Stx1B alone and Stx1B with any inhibitor are statistically significant (P < .01); no comparisons between any Stx2B condition are statistically significant (P > .05). Each experiment repeated at least 3 times with similar results.