PERSISTENCE OF A PERINATAL CELLULAR PHENOTYPE IN SUBMANDIBULAR GLANDSOF ADULT-RAT

In the perinatal submandibular gland (SMG) of the rat, Type I cells se crete protein C (89 KD) and Type III cells secrete B1-immunoreactive p roteins (20-30 KD); both cell types secrete protein D (175 KD). After the disappearance of both perinatal cell types from the maturing acini , only cells of the intercalated ducts (ID) show strong reactivity for the perinatal antigens. In adult ID, light and electron microscopic i mmunocytochemical analysis showed that most cells had either C or B1 r eactivity, a few had either C and D or B1 and D reactivities, and some cells were unreactive for all of the perinatal proteins. Occasional d usters of ''adult'' acini, however, were strongly positive for B1 and for D, and these dusters were negative for a typical adult acinar mark er, the glutamine/glutamic acid-rich proteins (GRP). Also seen in some preparations were a few anomalous acini with the histological appeara nce of sublingual (SLG) acini. These were negative for the perinatal a nd adult submandibular gland marker proteins but reactive with an anti body against SLG mucin. We suggest that the B1-positive acini in the a dult SMG consist of newly differentiated replacement cells that have a risen from the ID, and that the anomalous mucous acini are, phenotypic ally, SLG acini that have differentiated within the SMG parenchyma.