Regeneration of the rat submandibular glands after duct ligation

: The cytomorphologic changes associated with acinar cell recovery in the rat submandibular glands were examined by light and electron microscopic observation and immunohistochemical test using anti-bromodeoxyuridine antibody. Ligation of excretory ducts caused morphological disorganization of the gland parenchyma, with resultant disappearance of the acini, dilation of the ducts, pronounced fibrosis and infiltration of the inflammatory cells. At seven days after obstruction, the acinar cells shrunk and destroyed partly. However, the intercalated duct cells and the myoepithelial cells were unaffected by ligation. Immunohistochemically, bromodeoxyuridine (BrdU) labeled cells existed scatteringly in the original ducts through the period of duct ligation and unligation studied. In the glands after recanalization following 7 days of the duct ligation, the duct-like structures were recognized a progressive increase. There structures were significantly developed in number from 7 to 14 days after the unligation. However, the BrdU-containing nuclei were not almost found in the duct-like structures. At twenty one days after the removal of the obstruction, the regeneration of acinar cells was striking. At 28 days, the acini were almost normal size. In the unligated glands at 21 and 28 days, a variable number of BrdU-positive cells was found in acini. At this stage, the constituent cells of the duct-like structures occurred many vacuoles and a decrease in their secretory granules was marked. These cells were transformed into intercalated duct cells. These results suggest that the constituent cells of the duct-like structures are altered for intercalated duct cells. The regeneration of acinar cells is the result of cell recovery, not the result of de novo cell differentiation.