The uPA storage site in QPD platelets. (A) Immunogold labeling of uPA in QPD platelets, showing occasional uPA labeling in α-granules, with no significant labeling of the surface-connected canalicular system (SCCS), mitochondria (m), or plasma membrane. Inset shows a QPD platelet α-granule under higher magnification. Experiments were performed as outlined in “Immunoelectron microscopy.” (B) Deconvolved immunofluorescent images of QPD platelets, double immunolabeled with an antibody to uPA (red, left panels) and antibodies to TSP-1, VWF, or VEGF (green, middle panels) (merged images on right). Experiments were performed as outlined in “Immunofluorescent microscopy.” (C) Western blot of VEGF in pooled platelets from 20 healthy individuals (NPP), and in platelets from 4 QPD and 2 control individuals, evaluated after SDS-PAGE. Arrow indicates VEGF forms with lower mobility in QPD platelets.