Cytochemical studies on the localization of 5'-nucleotidase in the acinar cells of the rat salivary glands.

The cytochemical localization of 5'-nucleotidase (5'-AMPase), and its validity, were investigated in parotid and submandibular acinar cells of a rat. Biochemical determinations showed that adequate treatment with glutaraldehyde could minimize the loss of enzymatic activity, and that 5'-AMPase and non-specific alkaline phosphatase (beta-GPase) possessed different pH optima. The cytochemical distribution of the reaction products from the 5'-AMPase activity was distinct from those of beta-GPase. 5'-AMPase activity was localized on the surface membranes of acinar, ductal and myoepithelial cells of both salivary glands. beta-GPase activity was evenly distributed on the entire plasma membranes of myoepithelial cells and on the basal plasmalemma of acinar cells. The reaction products, which appeared on the luminal and lateral plasma membranes of the acinar cells, were presumed to reflect the presence of 5'-AMPase, while those on the myoepithelial surface and basal plasma membranes of the acinar cells demonstrated both 5'-AMPase and beta-GPase. The results indicate that 5'-AMPase activity can be utilized as a reliable marker enzyme of plasma membranes in the salivary acinar cells.