Effect of PDE3A inhibition by JF959602 on the initial rate of platelet arrest and detachment at sites of vascular injury following laser-induced endothelial cell injury. (A) Images from experiments using calcein-labeled platelets were manually colored for identification of individual platelets over time to demonstrate the dynamics of platelet accumulation at the site of vascular injury. Changes in the composition of platelets at the site of injury (arrow) indicates arrest and detachment of individual platelets. These analyses indicate that only 14% of platelets that arrest at the site of arteriolar injury are incorporated into the thrombus. (B) The initial rate of platelet arrest was quantified for 30 seconds following laser-induced injury by counting the number of calcein-labeled platelets that arrested for at least 1 second at the site of vascular injury. The presence of 1.2 mg/kg JF959602 (○) (n = 22) significantly decreased the initial rate of platelet arrest compared with the saline control (•) (n = 34). Error bars represent mean ± 1 SEM. (C) The initial rate of platelet detachment was quantified by counting the number of arrested calcein-labeled platelets that detached from the thrombus for 30 seconds following injury. The presence of 1.2 mg/kg JF959602 (○)(n = 22) significantly increased the initial rate of platelet detachment compared with the saline control (•)(n = 34). Error bars represent mean ± 1 SEM.