LOCALIZATION OF AN ECTO-ATPASE CELL-CAM-105 (C-CAM) IN THE RAT PAROTID AND SUBMANDIBULAR GLANDS

We investigated an ecto-ATPase/cell-CAM 105 (C-CAM), previously shown to be distinct from the Ca2+ pump, in rat parotid and submandibular gl ands. Polyclonal antibodies raised against the enzyme were employed us ing indirect immunofluorescence, peroxidase-anti-peroxidase (PAP), and electron microscopic immunogold labeling procedures to visualize the location of the enzyme. In the PAP-stained sections and with immunoflu orescence, labeling was observed on the luminal and lateral surfaces a nd the intercellular canaliculi of the acinar cells of both glands. Th e luminal surface of the intercalated ducts was brightly stained, wher eas those of the striated and excretory ducts were less prominently la beled. The basal surface of the acinar cells in the parotid gland and the lateral and basal surfaces of the duct cells were not labeled. App arent labeling was observed on the basal surface of the submandibular acinar cells. Electron microscopy revealed that for both glands the en zyme was primarily localized along the luminal border of the acinar ce lls, mainly in association with microvilli, with slightly less reactiv ity along the intercellular canaliculi and lateral borders and relativ ely little along the basolateral membranes. Gold labeling was also obs erved on the luminal borders of the intercalated and striated ducts. P ossible functions of the C-CAM include breakdown of ATP, stabilization of the microvillar membranes, cell adhesion, and involvement in secre tory mechanisms.