Cell Proliferation Activity in Duct-Ligated Submandibular Gland

Cellular proliferation activity in duct-ligated submandibular glands (SMGs) of rats were evaluated by using index of proliferating cell nuclear antigen (PCNA) immunostaining and 3H-thymidine incorporation. The normal SMGs showed a very low index (<0.1%) of PCNA immunostaining and 3H-thymidine incorporation in the acinar and all the ductal segments. On day 2 and 3 of duct ligation, index of PCNA staining and 3H-thymidine incorporation increased and reached a peak in degranulated granular convoluted tubules (GCTs), duct like structures (DLSs) and dilated excretory ducts (EDs). On day 5 to 10, the glands showed fibrous proliferation around the DLS, and cells in DLSs and dilated EDs had decreasing index of PCNA staining and 3H-thymidine incorporation. On day 14 and 21, the PCNA staining and 3H-thymidine incorporation had decreased and was mainly confined to the DLSs and basal cells of keratinizing epithelial masses. In the unligated SMG of the opposite side of the duct-ligated animals, proliferating cells were found mainly in the acinar compartment from the 2nd to 5th day of ligation.These results suggested that in case of acceleration of secretry function of SMG, secretory cells may proliferate as for the functional adaptation. However, in the case of obstructive lesions of SMG, GCT cells and ductal basal cells may have more potential for proliferation and these cells may be the major participant cells during glandular regeneration and possibly in the histogenesis of the majority of salivary gland tumors, if not all.