title: Changes in the number and distribution of myoepithelial cells in the rat parotid gland during postnatal development.
abstract: The mature rat parotid gland shows hardly any cell bodies of myoepithelial cells around the acini, only a few cell processes being visible. However, in the early postnatal period, the rat parotid gland shows many myoepithelial cell bodies around the acini, including the intercalated ducts. In order to clarify the reason for the disappearance of myoepithelial cells from the area around the acinus during postnatal development, changes in the number and distribution of myoepithelial cells in the rat parotid gland were examined histochemically and chronologically, with particular reference to cell proliferation and cell death. From day 7 to day 14, many myoepithelial cells showing a positive reaction with anti-actin antiserum were found around the acini and intercalated ducts, but thereafter the number of such cells decreased gradually, particularly around the acini, and had almost disappeared after day 35. BrdU/PCNA-positive myoepithelial cells surrounding the acini were easily detected on day 14, but disappeared by day 21, whereas BrdU/PCNA-positive acinar cells remained numerous even after day 21. TUNEL/ISEL staining showed no positive myoepithelial cells throughout the observation period. Transmission electron microscopy also demonstrated no myoepithelial cells with chromatin condensation characteristic of apoptosis through the observation period. These findings suggest that the main reason for the disappearance of myoepithelial cells from the area around the acinus during postnatal development is the large difference between the number of myoepithelial cells and that of acinar cells, because the acinar cells retain their proliferative activity even after myoepithelial cells have become quiescent.
authors.affiliation: Department of Histology, School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20 Fujimi, Tokyo 102-8159, Japan.
authors.forename: Toshiya
authors.initials: T
authors.lastname: Tsujimura
authors.forename: Rie
authors.initials: R
authors.lastname: Ikeda
authors.forename: Shigeo
authors.initials: S
authors.lastname: Aiyama
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002452:Cell Count; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008297:Male; D008854:Microscopy, Electron; D010306:Parotid Gland / Q000166:cytology* / Q000254:growth & development* / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar / Q000033:anatomy & histology / Q000254:growth & development*; D018987:Salivary Ducts / Q000166:cytology / Q000254:growth & development / Q000378:metabolism
chemical_list: D000199:Actins; D018809:Proliferating Cell Nuclear Antigen; D001973:Bromodeoxyuridine