Cc2^−/− platelets display enhanced α and dense granule release after stimulation with GPVI and CLEC-2–selective agonists, CRP and Rhod. (A) Surface expression of P-selectin as a marker of α granule release was determined for washed platelets stimulated by several agonists: (a) Thrombin (0.125-0.25 U/mL), PAR-4 agonist peptide (100-300 µM), (b) CRP (0.5-2.0 µg/mL), and (c) Rhod (0.6-1.2 µg/mL). Then they were stained with FITC-conjugated P-selectin mAb for wild-type, Cc1^−/−, and Cc2^−/− platelets. FITC-labeled samples were analyzed on an FACS Canto II flow cytometer. Results are representative of 3 independent experiments (*P < .05, **P < .01; n = 4). (B) Platelet-dense granule exocytosis measured by release of fluorescent quinacrine by flow cytometry. Washed platelets (1 × 10⁸/mL) were derived from both wild-type and Cc2^−/− mice and were stimulated with either no agonist or agonist. (a) Thrombin (0.125-1.0 U/mL) or PAR-4 agonist peptide (100-300 µM) or (b) CRP (0.25-4.0 µg/mL). (c) Wild-type, Cc1^−/−, and Cc2^−/− platelets were stimulated by Rhod (0.4-1.2 µg/mL). Samples were analyzed on an FACS Canto II flow cytometer. Data are reported as percentage quinacrine release and are representative of 4 independent experiments (*P < .05, **P < .01, ***P < .001; n = 4).