(A) Effect of echicetin and echistatin on HUVEC adhesion to immobilized vWF. HUVECs were preincubated with progressively increasing concentrations of echicetin and echistatin (an vβ3 antagonist) for 15 minutes on ice before being applied to a 96-well microplate previously coated with vWF as described in Materials and Methods. OD readings of the lysed cells indicated that about 45% of resting HUVECs adhered to immobilized vWF, and this value was used as 100% adhesion. (•) Echicetin; (▪) echistatin. The data represent the mean and SD of percentage of cell adhesion from four individual experiments. (B) Additive inhibition of echicetin and echistatin on HUVEC adhesion to immobilized vWF. HUVECs were preincubated with either 250 nmol/L echicetin (EC; lane 3), 50 nmol/L echistatin (ES; lane 4), or both 250 nmol/L echicetin and 50 nmol/L echistatin (EC + ES; lane 5) and were then applied onto a vWF-coated plate. For a negative control (lane 1), BSA-coated wells were used. Lane 2 represents HUVEC adhesion to vWF in the absence of inhibitors.