PAR1 antagonists decrease the platelet angiogenic potential. (A) VEGF concentration in releasate generated from the platelets resting or exposed to MCF-7 cells with and without preincubation with PAR1 antagonist 161. (B) Quantification of branch points generated by the releasate from resting platelets or platelets exposed to MCF-7 cells with and without preincubation with PAR1 antagonists. (C) Representative images of capillary tube formation generated from the releasate of resting platelets or platelets exposed to MCF-7 cells with and without preincubation with PAR1 antagonists. *P < .05. Bar represent 100 mm. (D) VEGF concentration in the releasate generated from the platelets resting or exposed to MCF-7 cells with and without preincubation with UFH and PAR1 agonist, TFLLR-NH2. (E) VEGF concentration in the releasate generated from the platelets resting or exposed to MCF-7 cells with and without preincubation with LMWH and PAR1 agonist, TFLLR-NH2. (F) VEGF concentration in the releasate generated from the platelets resting or exposed to MCF-7 cells with and without preincubation with fondaparinux and PAR1 agonist, TFLLR-NH2. (G) Quantification of branch points generated by the releasate from resting platelets or platelets exposed to MCF-7 cells with and without preincubation with PAR1 agonist TFLLR-NH2. (H) Representative images of capillary tube formation. (I) To determine if the anticoagulants disrupted cleavage of PAR1, the percentage of uncleaved PAR1 on the surface of the platelet was measured using the antibody SPAN12 by flow cytometry.