Figure 1.

Oxygen radical generation by platelets activated by physiological stimuli collagen and thrombin. Washed human platelets were prepared as described. Collagen was tested at concentrations ranging from 1 to 30 μg/mL (A and C), while thrombin was tested from 0.03 to 1 unit/mL (B and D). Electron paramagnetic resonance (EPR) was used to measure oxygen radicals formation as 1-hydroxy-3-methoxycarbonyl-2, 2, 5, 5-tetram-ethylpyrrolidine (CMH) oxidation rates [32.7 and 37.3 attomoles per platelet per minute (min), respectively] (A and C) and aggregation was simultaneously assessed by turbidimetry (B and D). For either technique, representative examples are shown in top panels, while quantification is shown in the bottom panels. Aggregation curves up to 5 min are shown, while EPR resonance readings were taken after 10 min of stimulation. Examples of EPR traces and aggregation curves are representative of 4 independent experiments. Statistical analysis was performed by one-way ANOVA with Bonferroni post-hoc test. *P<0.05 compared to resting platelets. N=4 for (A-D).