Role of MRP4 in whole-blood platelet adhesion ex vivo. Whole blood from MRP4^−/− and WT mice was collected on PPACK (80 μM)/lepirudin (100 U/mL). Dioc6-labeled treated blood was perfused over a fibrillar collagen matrix (50 μg/mL) at a shear rate of 1800 seconds⁻¹ for 3 minutes. (A) The formation of Dioc6-stained thrombi was recorded with a CoolSnap camera on a Leica DM IRB microscope. Images are representative of a minimum of 7 experiments in each group. (B) The mean fluorescence intensity was quantified with ImageJ software. Each point, corresponding to an independent experiment (n ≥ 7), represents the mean fluorescence intensity of at least 8 fields. (C) Nucleosome content was quantified in plasma prepared from the flow chamber effluent, using an enzyme-linked immunosorbent assay cell-death detection kit. One arbitrary unit (a.u.) of nucleosomes corresponds to the average amount of nucleosomes contained in plasma from a minimum of 8 WT control animals (***P < .0001).