Sialidase-treated Adam17^ΔZn/ΔZn platelets are rapidly cleared from the circulation. (A) CMFDA-labeled fresh room temperature Adam17^+/+ and Adam17^ΔZn/ΔZn platelets were treated with sialidase (5 mU/mL; filled symbols) or left untreated (open symbols) were infused intravenously into Adam17^+/+ mice (10⁸ platelets/10 g of body weight). Blood was drawn at the indicated time points, and the platelets were immediately analyzed by flow cytometry. Results are expressed as the mean percentage of CMFDA-labeled platelets ± SEM. The percentage of CMFDA-positive untreated Adam17^+/+ platelets at 5 minutes after transfusion was set as 100%. Each point represents 4 mice; ***P < .001. Sialidase-treated Adam17^+/+ and Adam17^ΔZn/ΔZn were compared. (B) Flow cytometric analysis of terminal β-galactose on glycoproteins, as detected with ECL FITC-labeled lectin. Lectin binding to Adam17^+/+ or Adam17^ΔZn/ΔZn platelets treated or not with α2-3,6,8,9-sialidase. The ratio of mean fluorescence intensity binding to untreated Adam17^+/+ platelets is shown. Histograms report the mean ± SEM of 3 separate experiments. *P < .05, **P < .01, and ***P < .001. (C) GPIbα, GPV, and α_IIbβ₃ surface expression was assessed by flow cytometry. Adam17^+/+ (not shown) and Adam17^ΔZn/ΔZn platelets were treated with sialidase (5 mU/mL; ■) or not (□). Results are expressed relative to the amount of GPIbα on Adam17^ΔZn/ΔZn platelets (mean percentage of relative to control ± SEM; n = 3).