cAMP/PKA signaling modulates the activation of RhoA. (A) Washed platelets (5 × 10⁸ platelets per milliliter) were stimulated with thrombin (0.05 U/mL) for 1 minute in the presence or absence of Y27632 (10 µM), BAPTA-AM (20 µM), 8-CPT-6-Phe-cAMP (50 µM), or PGE₁ (100 nM), and activated RhoA (GTP-RhoA) was assessed by using a pull-down assay with Rhotekin-RBD beads. (i) Representative immunoblots from 3 independent experiments. (ii) Densitometric analysis of activated RhoA (GTP-RhoA) of 3 different experiments. *P < .05 compared with thrombin only. (B) Same as in (A), except platelets were treated with PKA inhibitors Rp-8-CPT-cAMPS (500 µM)/KT-5720 (20 µM) for 15 minutes prior to addition of thrombin and PGE₁. (C) Same as in (B), except platelets were treated with Rho Activator I (30 µM) for 2 minutes instead of thrombin. (D) Same as in (B), except platelets were treated with oxLDL (50 μg/mL) for 15 seconds instead of thrombin.