Inhibition of platelet aggregation by OxHDL in response to thrombin, collagen, and ADP. (A) Human platelets isolated by gel filtration (2.5 × 10⁸/mL) containing 2 mM Ca²⁺ and 1 mM Mg²⁺ were incubated with 200 μg/mL HDL, OxHDL, or LDL and 1 mg/mL of HDL for 2 minutes at 37°C, followed by stimulation with 0.1 U/mL thrombin. Platelet aggregation was monitored in a Lumi-Aggregometer. (B) Platelets were incubated with 200 μg/mL HDL or OxHDL for 5 minutes at 37°C and stimulated with 5 μg/mL collagen type I. (C) Platelets in the presence of 300 nM of human fibrinogen were incubated with 200 μg/mL HDL or OxHDL for 5 minutes at 37°C and stimulated with 10 μM of ADP. (D) Quantification of the data (means ± SD) panels A-C from 5 independent experiments. NA indicates no addition. *P < .001.