PECAM-1^−/− platelets have a lower threshold for release of dense granular contents in response to stimulation through GPVI collagen receptor.

Platelets isolated from wild-type (open bars) and PECAM-1^−/− (closed bars) mice were stimulated with varying concentrations of GPVI-specific agonists, including fibrillar collagen in absence of Mg²⁺ (A) and CRP (B), or with thrombin (C). The amount of ATP released was measured using the luciferin–luciferase assay as described in “Materials and methods.” The assays were performed in triplicate, and the results are expressed as the mean of triplicate measurements ± SD. Similar results were obtained from 3 independent experiments. Note that the release of dense granular contents in response to stimulation with low concentrations of GPVI-specific agonists was elevated in PECAM-1^−/− platelets compared to the wild-type platelets.