Evaluation of SNAP-23, syntaxin-2, and VAMP-3 on the surface of resting and activated platelets using flow cytometry. Gel-filtered platelets were exposed to either buffer alone, SFLLRN, or PMA and subsequently stained with nonimmune IgG or an IgG directed at either (A) SNAP-23, (B) syntaxin-2, or (C) VAMP-3. Samples were subsequently analyzed by flow cytometry. Values are reported as percent of control compared with signal detected in unstimulated samples exposed to nonimmune antibodies. Error bars represent the standard deviation of 3 to 6 independent experiments. Histograms were derived from analysis of platelets exposed to buffer alone (), SFLLRN (), or PMA () and then stained with antibodies directed at (D) SNAP-23, (E) syntaxin-2, or (F) VAMP-3.