CELL-POPULATION CHANGES DURING ATROPHY AND REGENERATION OF RAT PAROTID-GLAND

Limited data exist regarding the changes in number and location of myo epithelial cells during salivary gland atrophy and regeneration. Throu gh the use of double immunohistochemical labeling for muscle-specific actin and amylase coupled with morphometric analysis, this study inves tigated the changes in distribution and proportion of cell types durin g salivary gland atrophy/regeneration phases in a model previously use d to study proliferation in rat parotid gland. The double immunohistoc hemical labeling clearly showed the changes in proportion of cell type s in the atrophying and regenerating glands. The morphometric analysis showed that the relative myoepithelial area increased (as did the int ercalated duct and striated duct areas) as the gland atrophied. Myoepi thelial cells occupied 19.0% of the total epithelial area by day 7 of atrophy, up from 2.7% in the resting gland. Regeneration of acinar cel ls was obvious 1 day after duct release. The myoepithelial cell area d ecreased to 4.3% of the total epithelial area by day 74 of regeneratio n; this value was higher than the percentage of area in the resting gl and (p = 0.02). The relative areas of acinar, striated duct, and inter calated duct cells returned to resting levels after 14 days of regener ation. The morphometric and histologic results of this study show that the parotid gland is capable of regenerating to essentially normal an atomic condition after 7 days of gland atrophy and then 14 days of reg eneration. Each type of cell, however, responded to the atrophy and re generation differently. Atrophy of salivary glands from radiation ther apy, Sjogren's syndrome, or sialadenitis is an important clinical prob lem. Study of the salivary gland response to atrophy and regeneration may provide a framework for designing strategies for the radioprotecti on of salivary glands or methods by which to treat or reverse the effe cts of gland atrophy.