Ultrastructural features of goat oviductal secretory cells at follicular and luteal phases of the oestrous cycle

The aim of the present study was to investigate the ultrststructure of secr etory cells in the various regions of the goat oviduct during the follicula r and luteal phases of the oestrous cycle. Daring the follicular phase in t he fimbriae, the secretory cells contained small secretory granules with el ectron-dense matrices. In the luteal phase, the secretory granules disappea red and cytoplasmic protrusions, extending beyond the luminal border of the ciliated cells and often containing the nucleus, were predominant. During the follicular phase in ampullary secretory cells, numerous secretory granu les with moderately electron-dense matrices were present in the supranuclea r cytoplasm and exocytosis of secretory granules was observed. The number o f secretory granules was dramatically reduced in the ampullary secretory ce lls at the luteal phase. Conspicuous cytoplasmic protrusions of secretory c ells were observed similar to those of the fimbrial epithelium. Isthmic cel ls were almost free of secretory granules and lysosome-like bodies were fou nd both at the follicular and luteal phases. In conclusion, our ultrastruct ural observations of goat oviduct revealed marked cyclic changes in the ult rastructural features of secretory cells and the ultrastructural features a nd the numbers of secretory granules were distinctive for each particular s egment.