LOCALIZATION OF PEROXIDASE ACTIVITY IN THE DEVELOPING SUBMANDIBULAR GLAND OF NORMAL AND ISOPROTERENOL-TREATED RATS

Abstract

The localization of peroxidase activity was studied in the developing submandibular gland of normal and isoproterenol-treated rats using a diaminobenzidine-H₂O₂ method. During postnatal development peroxidase activity was localized in the proacinar and acinar cells. The proacinar cells were characterized by the presence of polymorphic secretory granules that gave a strong peroxidase reaction, particularly in the glands of 1-day-old rats. In addition to the secretory granules, enzyme activity was demonstrated in the rough endoplasmic reticulum and nuclear envelope. The terminal tubule cells and duct cells were devoid of peroxidase activity. The secretory granules in the fully developed acinar cells revealed little or no enzyme activity. Isoproterenol stimulated the secretion of the peroxidase-positive granules from the proacinar cells. The stimulation was followed by a reaccumulation of peroxidase-positive secretory material. During this process enzyme activity was demonstrable in the Golgi complex. Isoproterenol had no effect on the terminal tubule cells. A less effective depletion of the secretory granules from the proacinar cells was seen after pilocarpine administration. Chronic administration of isoproterenol to 5-day-old rats led to an acceleration of the differentiation of acinar cells and to a hypertrophy of the gland, without significant change in the localization of peroxidase activity.