Major secretion regulators are unchanged in the absence of SNAP23. (A) Unstimulated platelets at 200 × 109/L were lysed and proteins were run on sodium dodecyl sulfate–polyacrylamide gel electrophoresis, before transfer to polyvinylidene difluoride membrane (Immobilon FL), and probed as indicated. Membranes were imaged on a LiCor Odyssey CLx with species-appropriate near-infrared (700/800 nm)–conjugated secondary antibodies. Data are representative of at least 3 independent experiments. (B) Densitometric analysis of platelet secretion regulators or granule cargo proteins. Data are expressed as a percent of the wild-type (WT) average per blot. Data were compared by 2-way analysis of variance (ANOVA) with Sidak’s multiple comparisons test. No data were significant. Munc13-4, VAMP8; WT (n = 14), knockout (KO) (n = 11). CD62-P (P-selectin), Syntaxin 11, SNAP29; WT and KO (n = 8). Munc18b, STXBP5, VAMP7; WT (n = 5), KO (n = 4). PECAM, Syntaxin 8; WT (n = 5), KO (n = 3).