Fig. 3. Colocalization of Rab27B, Slp4-a and Slac2-c with VAMP-2, a secretory granule marker, in rat parotid acinar cells. Each section was immunostained for Rab27B (A,D), Slp4-a (B,G), or Slac2-c (C,J) and double-stained for VAMP-2 (E,H,K) to confirm the presence of secretory granules in the apical regions of the acinar cells. The merged images are shown in F, I and L. Note that Rab27B, Slp4-a and Slac2-c were mainly colocalized with VAMP-2 on secretory granules that are close to the apical plasma membrane of the acinar cells (F,I,L, respectively). The cells are outlined in white; ap, apical plasma membrane. Scale bars: 5 µm.