Distribution of lectin-binding glycosidic residues in the hamster follicular oocytes and their modifications in the zona pellucida after ovulation

In the present study, we have employed a battery of colloidal gold-tagged l ectins as probes in conjunction with quantitative analysis to demonstrate t he distribution and changes of carbohydrate residues in the hamster zona pe llucida (ZP) during ovarian follicular development and during transit of th e oocyte through the oviduct after ovulation. High-resolution lectin-gold c ytochemistry performed on thin sections of LR White-embedded ovaries reveal ed a moderate to strong reactivity to WGA, PNA, DSA, AAA, and MAA over the entire thickness of the ZP of ovarian oocytes at different stages of follic ular development. Labeling intensity over the ZP progressively increased as follicles matured in the ovary. In parallel, there was an association of l abeling by gold particles with cortical granules, stacks of Golgi saccules, and complex structures called vesicular aggregates in the oocyte proper es pecially during the late stages of follicular growth. In contrary, labeling with each of HPA, DBA, and BSAIB(4) was absent in the ovary but was found to be localized over Golgi complexes and secretory granules in the non-cili ated secretory cells of the oviduct. When ovulated oocytes were labeled wit h each of HPA, WGA, RCA-1, PNA, DSA, BSAIB4, AAA, MAA, and DBA, the ZP and several organelles in the oocyte proper presented a differential distributi on of lectin-binding sites. Quantitative analysis was also performed on lab eling by lectin-gold complexes that bind specifically to the ZP of mature f ollicular and ovulated oocytes. Quantitative evaluation revealed heterogene ous labeling between the inner and the outer zone of the ZP. A significant increase in the labeling densities in both inner and outer ZP was noted whe n tissue sections of ovulated oocytes were labeled with RCA-1 or AAA. Tissu e sections of ovaries labeled with WGA demonstrated a significant increase in the density of labeling in the outer layer of the ZP. Labeling by PNA, D SA, and MAA, however, showed a significant decrease in both the inner and o uter portions of the ZP. Together, these results suggest that in the hamste r, glycoproteins carrying specific sugar residues are added to the ZP of ov arian follicles during the early stages of folliculogenesis and are process ed through a common secretory machinery, and that there is a significant ch ange in both the sugar moieties and distribution of glycoproteins in the ZP following ovulation. Our results also showed that the hamster oviduct play s an important role in contributing certain glycoproteins to the ZP suggest ing that the sugar moieties of these oviductal glycoproteins may have funct ional significance in fertilization. Mol. Reprod. Dev. 60: 517-534, 2001. ( C) 2001 Wiley-Liss, Inc.