Immunohistochemical localization of dipeptidyl aminopeptidase (DAP) IV in the rat submandibular gland during postnatal development.

The localization of dipeptidyl aminopeptidase (DAP) IV in the rat submandibular gland during postnatal development was studied immunohistochemically using the unlabeled antibody enzyme method. Cryostat sections of rat submandibular glands were examined in animals 1 to 50 days old. In the first postnatal week, faint immunoreaction was detected in the apical region of the cytoplasm of terminal tubules. During the second postnatal week the reaction was gradually restricted to the luminal region of terminal tubules or developing acinar cells, and its intensity increased. The most striking change of the enzyme localization was observed in 15-day-old rats. At this time, DAP IV was confined to the luminal and lateral membranes of differentiated acinar cells and to the luminal membranes of intercalated and striated duct cells. This localization pattern was similar to that of the adult animal. DAP IV activity in the gland was also measured biochemically during the postnatal development. The results were in agreement with those of the immunohistochemical study. These results suggest that the localization of DAP IV is closely related to the postnatal differentiation and proliferation of acinar cells.