Ultrastructural and ultracytochemical features of secretory granules in the ampullary epithelium of the hamster oviduct.

The epithelium of mammalian oviducts consists mainly of ciliated and non-ciliated secretory cells. In some mammals, secretory products originating from oviductal secretory cells have been shown to bind to the surface of, or accumulate within, ovulated eggs and/or developing embryos. These findings suggest that the secretions of the oviductal epithelial cells may play an important role in reproductive and developmental events that occur in the oviduct. In the present study, ultrastructural and cytochemical features of secretory cells in the hamster ampullary epithelium were shown by routine electron microscopy, lectin-gold cytochemistry and both conventional freeze-fracture and rapid-freezing techniques with special reference to the organizational aspects of their secretory granules. The use of ferrocyanide-reduced osmium tetroxide as a post-fixative in the Epon embedment of ampullary tissue samples also proved to be advantageous especially in revealing the carbohydrate contents of certain cellular compartments. The most conspicuous characteristic of the secretory cells, based on their staining property, was the presence of two types of secretory granules: those with a homogeneous electron-dense matrix and those with an electron-lucent matrix. Under favorable conditions, distinct features of the organizational arrangement of a crystalline lattice inside the secretory granules were also revealed. This well organized crystalline lattice shown in sections of Epon-embedded oviductal tissue was confirmed by examination of replicas of freeze-fractured oviducts prepared by the rapid-freezing technique. We also demonstrated with high resolution lectin-gold cytochemistry the intracellular distribution of lectin-binding glycoconjugates in the secretory cells of the hamster oviductal ampulla often in a linear array following the crystalline lattice. The results obtained in this study, taken together, provide insight into a possible link of the internal topographical features of oviductal secretory granules along with the cytochemical properties of their contents to the anticipated regulatory mechanism underlying their process of secretions.