Persistence of a perinatal cellular phenotype in submandibular glands of adult rat.

Abstract

In the perinatal submandibular gland (SMG) of the rat, Type I cells secrete protein C (89 KD) and Type III cells secrete B1-immunoreactive proteins (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 immunocytochemical analysis showed that most cells had either C or B1 reactivity, a few had either C and D or B1 and D reactivities, and some cells were unreactive for all of the perinatal proteins. Occasional clusters of "adult" acini, however, were strongly positive for B1 and for D, and these clusters were negative for a typical adult acinar marker, the glutamine/glutamic acid-rich proteins (GRP). Also seen in some preparations were a few anomalous acini with the histological appearance of sublingual (SLG) acini. These were negative for the perinatal and adult submandibular gland marker proteins but reactive with an antibody against SLG mucin. We suggest that the B1-positive acini in the adult SMG consist of newly differentiated replacement cells that have arisen from the ID, and that the anomalous mucous acini are, phenotypically, SLG acini that have differentiated within the SMG parenchyma.

Salivary Glands: A Paradigm for Diversity of Gland Development

“…4; Moreira et al, 1990). This exclusivity has since been confirmed more generally by light microscopic immunocytochemistry (Man et al, 1995 labeled cells were in positions near acini. This was particularly common for cells that were reactive for Protein C ( Fig.…”

“…This was particularly common for cells that were reactive for Protein C ( Fig. 3; Man et al, 1995). The secretory granules of the granular intercalated duct cells of adult female mouse submandibular glands appear to contain consistently low levels of acinar cell-specific mucin (Denny et al, 1988).…”

“…Although its co-localization with BI has not yet been established by studies using the two antibodies, the morphological distribution of the CSPI-labeled intercalated duct cells and the absence of CSPI reactivity from those intercalated duct cells that appear similar to Type cells suggest a cellular distribution that is at least similar to that of the BI proteins (Girard et al, 1993). The functional significance of the maintenance of high levels of CSPI in the intercalated duct of adult male glands is unclear (8) B I-REACTIVE ACINI Electron microscopic studies failed to reveal Bl-labeling in adult acini (Ball et al, 1988a;Moreira etal., 1991), however, the greater areas visualized in the light microscopic procedures showed occasional groups of acini with high levels of Bl -reactivity (Man et al, 1995). These were highly atypical adult acini, having all of the immune reactivities of neonatal Type Ill cells, including high levels of Bl and D reactivity, no Protein C labeling, and no reactivity for the mature acinar cell protein, GRP They were smaller than the typical adult acini and often located at the tips of lobules It was suggested that these might be replacement acini going through a stage of differentiation similar to that seen during normal embryogenesis and neonatal development, before becoming mature acinar cells (Man et at., 1995).…”

“…The functional significance of the maintenance of high levels of CSPI in the intercalated duct of adult male glands is unclear (8) B I-REACTIVE ACINI Electron microscopic studies failed to reveal Bl-labeling in adult acini (Ball et al, 1988a;Moreira etal., 1991), however, the greater areas visualized in the light microscopic procedures showed occasional groups of acini with high levels of Bl -reactivity (Man et al, 1995). These were highly atypical adult acini, having all of the immune reactivities of neonatal Type Ill cells, including high levels of Bl and D reactivity, no Protein C labeling, and no reactivity for the mature acinar cell protein, GRP They were smaller than the typical adult acini and often located at the tips of lobules It was suggested that these might be replacement acini going through a stage of differentiation similar to that seen during normal embryogenesis and neonatal development, before becoming mature acinar cells (Man et at., 1995). In what may be analogous structures, acini composed partially or entirely of granular intercalated duct cells were observed in adult female mouse submandibular glands (Denny et ai., 1990a).…”

“…The question remains to be resolved. (Man et al, 1995). (Yamashina and Barka, 1974;Moreira et al, 1990, 1993Girard et al, 1993 (Chang, 1974), and the quantity of Protein C decreases to very low levels after 20 days .…”