Effect of different inhibitors on platelet adhesion and aggregation on immobilized VWF. Platelets (PLTS) loaded with FLUO 3–AM were suspended into homologous washed red cells and plasma at the indicated final counts and perfused over immobilized VWF for 90 seconds at the wall shear rate of 3000 s^–1. (A) Representative single-frame images demonstrating aggregate formation as a function of platelet count. The bar graphs indicate the percentage (relative surface distribution) of single platelets or aggregates classified according to their surface area: (i) single platelets (2 μm2-13 μm2); (ii) microaggregates (14 μm2-50 μm2); (iii) small aggregates (51 μm2-200 μm2); and (iv) large aggregates (> 200 μm2). Error bars indicate ±95% confidence intervals. (B) Effect of distinct inhibitors on the relative surface distribution of single platelets and aggregates. Before perfusion, the reconstituted blood was incubated for 10 minutes at 37°C with the PI 3-K inhibitor wortmannin (final concentration, 100 nM), or the cyclooxygenase 1 inhibitor ASA (400μM), or the P2Y₁ ADP receptor inhibitor MRS2216 (12.5 μM), or the P2Y₁₂ ADP receptor inhibitor AR-C69931MX (1 μM). The results represent the mean plus or minus the 95% confidence intervals of 3 separate experiments performed at each of the indicated platelet counts. The asterisk indicates values that are significantly different from the corresponding control (*P < .01; Student t test).