IMMUNOHISTOCHEMICAL ANALYSIS OF THE PROLIFERATIVE CAPACITY OF DUCT AND ACINAR-CELLS DURING LIGATION-INDUCED ATROPHY AND SUBSEQUENT REGENERATION OF RAT PAROTID-GLAND

To study the proliferative capacity of salivary gland, an animal model of regeneration was developed. A clamp, which induced atrophy in parotid gland by obstructing the main excretory duct but allowed restoration of duct patency following removal, was implanted in a series of rats. When it was removed (Day 7), the weight of the glands was reduced by 50% and acinar cells had decreased from 93.8% to 8.2% of total cell population. Regeneration occurred rapidly following removal of the clamp. The number and location of cycling intercalated, striated, and excretory duct cells and acinar cells were monitored using an antibody to proliferating cell nuclear antigen (PCNA). All cell types were induced to cycle but the predominant cell to cycle was the acinar cell. During regeneration the number of PCNA+ acinar cells increased 38.7-fold from steady-state values. Results demonstrate that acinar cells have a significant potential for cycling, contrary to current histogenetic theories of salivary gland tumourigenesis which exclude acinar cells as potential progenitor cells on the grounds of their putative limited cycling capacity.