P-selectin exposure or JON/A binding on resting and activated platelets. Whole blood was incubated with buffer, convulxin (Cvx, 2.5 µg/mL), rhodocytin (rhodo, 50 nM), or TRAP4 (1000 µM) for 15 minutes at room temperature before measurement of P-selectin or JON/A (GPIIbIIa active form) exposure at the platelet surface. (A) Experiments performed in VavCre/JAK2^V617F mice (KI) and their controls (WT). ***P < .0001. (B) Experiments were performed in SCLCreER^t/JAK2^V617F mice at different times after administration of tamoxifen (white squares) or vehicle (black circles), incubated with convulxin (i) or rhodocytin (ii). (C) Surface expression of the active form of integrin αIIbβ3 (JON/A) was quantified on SCLCreER^t/JAK2^V617F platelets (TM) activated in whole blood by 3 doses of convulxin (0.5, 1, and 2.5 µg/mL) at different times after administration of tamoxifen.