Immunoelectron microscopy of PAI-1 in catecholamine storage vesicles. (A-C) PC12 cells were prepared for immunoelectron microscopy as described in “Immunoelectron microscopy of PAI-1 in PC12 cells and chromaffin granules.” PAI-1 antigen was detected in PC12 cells as gold particles in catecholamine storage vesicles using specific rabbit anti–rat PAI-1 IgG and goat anti–rabbit IgG conjugated to 10-nm colloidal gold particles (arrowheads in panels A and B). Controls (C) indicated a paucity of immunolabeling when normal rabbit IgG was used as the primary antibody. The bar in panel A corresponds to 200 nm, the bars in panels B & C to 100 nm. Magnification: A, 48 000; B-C, 110 250. (D-E) Isolated bovine chromaffin vesicles were prepared for PAI-1 immunoelectron microscopy as described in “Cells and tissues.” PAI-1 antigen was detected in isolated bovine chromaffin vesicles as gold particles using specific rabbit anti–rat PAI-1 IgG and goat anti–rabbit IgG conjugated to 10-nm colloidal gold particles (D). Controls (E) indicated a paucity of immunogold staining when rabbit IgG was used as the primary antibody. The bars in panels D & E correspond to 100 nm. Magnification: 164 000.