Regional variations in the ultrastructural features of secretory cells in the rat oviductal epithelium

Abstract

In mammals, the oviductal secretory cells and their secretions play important roles in reproductive and developmental events. Therefore, many electron microscopic studies of mammalian oviductal epithelial cells have been performed. The secretory cells in various regions of the rat oviduct during the estrous cycle were examined by transmission electron microscopy. In the fimbriae, the secretory cells contained small secretory granules with moderately electron-dense matrices and many large bodies that resembled lipid droplets. In the ampullar cells, small secretory granules with moderately electron-dense matrices were observed in the apical cytoplasm. In the isthmus, the secretory cells contained numerous secretory granules with moderately electron-dense matrices. Electron-dense areas were frequently observed in many of the granules of the isthmic cells. Vesicles, partially filled with a dense substance, frequently were observed in the isthmic cells and occasionally in the ampullar cells. Very long stereocilia projected from the surfaces of the isthmic secretory cells into the lumen. Exocytosis of the secretory granules was observed. In addition, there was evidence to suggest the release of the bodies that resembled lipid droplet occurred. Cysts and ciliated vacuoles that appeared to be intraepithelial were frequently observed in the fimbrial and ampullar epithelia. No dramatic changes in the relative numbers of ciliated and secretory cells in any oviductal segment were observed during the estrous cycle. Our ultrastructural observations of the rat oviduct revealed marked regional variations in the morphological features of secretory cells. These results may provide insight into regional and cellular differences in the function of the rat oviduct.