Kinetic analysis of platelet accumulation in thrombi following laser-induced endothelial cell injury in the presence of JF959602. (A) The kinetics of platelet accumulation after infusion of saline was examined by monitoring the fluorescent intensity of the thrombi. The kinetic curve was constructed based on the median value of platelet accumulation at 300 different time points of 33 independent pairs of injuries (heavy black line). A best-fit curve was fitted to represent the data (narrow black line). Three phases were assigned to the dynamic process of platelet accumulation. In the net positive phase, platelets are recruited into growing thrombi for approximately 90 seconds until maximum platelet accumulation is achieved. In the net negative phase, there is a net loss of platelets from thrombi. During the constant phase of thrombus formation, platelet content in thrombi stabilizes. (B) Inhibition of PDE3A activity by the infusion of either 0.3 mg/kg (n = 37, green lines) or 1.2 mg/kg JF959602 (n = 30, pink lines) resulted in suppression of platelet accumulation at all time points when compared with saline control (n = 33, black lines). The pattern of platelet accumulation, however, remained unchanged. (C) Rate of platelet accumulation into thrombi over time in the presence of JF959602 was obtained by plotting the derivative of the kinetic curve illustrated in panel B. JF959602 was found to decrease the maximal rate of platelet accumulation without affecting the time for thrombosis to reach the maximum rate. Similarly, JF959602 had almost no effect on the time to maximal platelet accumulation, as indicated by the point at which the rate of platelet accumulation intersects the ordinate.