PECAM-1^−/− platelets show hyper-aggregation in response to stimulation with GPVI-specific agonists.

Murine platelets were isolated from wild-type (WT) and PECAM-1^−/− (KO) mice, washed, and resuspended at a concentration of 2.5 × 10⁸ platelets/mL. Stirred platelets (200 μL) were exposed to fibrillar collagen in absence of Mg²⁺ at a concentration of 1 μg/mL (A) or 10 μg/mL (B), to CRP at a concentration of 0.5 μg/mL (C) or 5 μg/mL (D), or to thrombin at a concentration of 0.1 (E) or 1 (F) U/mL. Changes in light transmission of the stimulated platelet suspension were measured in an aggregometer. Similar results were obtained with 5 separate platelet preparations. Note that compared to wild-type platelets, PECAM-1^−/− platelets showed hyper-aggregation in response to stimulation with low concentrations of GPVI-specific agonists but not in response to stimulation with high concentrations of the same agonists or thrombin.