Immunocytochemical studies of major gap junction proteins in rat salivary glands.

We examined protein components of the gap junctions between acinar cells of the parotid, sublingual and submandibular glands of the rat, using type-specific antibodies directed against major gap junction proteins, connexin32 (Cx32) and connexin26 (Cx26). Double-immunofluorescence microscopy revealed that fluorescent spots of both connexins in the parotid and sublingual glands were distributed between the apposed regions of acinar cells. They appeared together, or were co-localized. The intensity of the Cx26-associated fluorescent signals was relatively weak in the submandibular glands compared with the other glands and was absent from some acini. When present, these spots were always co-localized with Cx32 immunoreactive positive spots. The results suggest that Cx32 and Cx26 in rat salivary glands are colocalized within the same gap junctional plaques when simultaneously expressed by the same acinar cells.