Electron microscopic observations of vaginal development in untreated and neonatally estrogenized balb/c Crgl mice

Abstract

Abstract Light and electron microscopic examinations of developing Mullerian vaginae were performed on untreated and neonatally estrogenized mice 1 to 12 days old. Vaginae of 1‐day‐old mice have an undifferentiated, pseudostratified columnar epithelium which slowly differentiates in untreated mice into an apparently mucus‐secreting epithelium. By day 12 the rough endoplasmic reticulum (RER), Golgi, and secretion granules are poorly developed features of the apical epithelial cells. In contrast, the stromal cells develop prominent RER and Golgi zones which in part are involved in the synthesis and secretion of collagen, which accumulates in the intercellular spaces. The effect of estradiol on developing vaginal epithelium is observed after 24 hours of exposure as an increase in RER and the Golgi. Estradiol (E) accelerates the differentiation of mucus‐secreting apical epithelial cells, whose apices become filled with secretory granules, and also promotes the formation of a cornifying epithelium from the underlying basal cells. This latter process is associated with an increase in cellular proliferation, an increase in the occurrence of desmosomes and associated tonofilaments, and the development of extensive interdigitation of plasma membranes. In untreated and E‐treated mice, the vaginal epithelium is separated from the stroma by a continuous, intact basal lamina. Transport of basal laminar material appears to occur via the processes of endo‐ and/or exocytosis in adjacent epithelial and stromal cells.