Changing myoepithelial cell distribution during regeneration of rat parotid glands.

The distribution of the myoepithelial cells during regeneration of the rat parotid gland after atrophy induced by one week of parotid duct ligation wa s investigated by immunohistochemistry for actin and transmission electron microscopy (TEM). Immunohistochemically, residual ducts were surrounded by actin-positive cells when clips were removed from the duct. Three days late r, most of the newly termed acini originating from the residual ducts were also embraced by actin-positive cells. After 10 days, actin-positivity tend ed to be seen as dots around acini that decreased in number day by day. On day 21 actin-positive cells mainly surrounded intercalated ducts with only a few positive reactions identified at the acinar periphery. Electron micro scopically, residual ducts and newly formed acini were peripherally embrace d by myoepithelial cells before day 5. After day 7, shift of myoepithelial cells from the periphery of acini to the duct-acinar junctional region was identified. Then few myoepithelial cells were identified at the periphery o f acini. These observations indicate that myoepithelial cells migrate from the acinar periphery to the duct-acinar junctional region during rat paroti d regeneration, and that such behaviour is closely related to that seen dur ing rat parotid development.