Inhibitors of glycoprotein biosynthesis block fertilization in the hamster

The nature and control of changes in surface carbohydrates in capacitating hamster spermatozoa were analysed by using five inhibitors of glycoprotein biosynthesis in an in vitro fertilization system. Epididymal spermatozoa were treated with amphomycin, bacitracin, tunicamycin, 2‐deoxyglucose, and 2‐deoxy‐2‐fluoro‐D‐glucose either during the entire period of capacitation or briefly at the end of capacitation before exposing to Con A‐coated agarose beads or hamster eggs with or without their zonae pellucidae. Untreated 4½‐5‐hr spermatozoa exhibited nearly 100% fertilization and became bound to Con A‐agarose beads mainly along the length of their flagellae, resulting in the formation of clumps on the beads. In the presence of inhibitors of glycosylation, spermatozoa did not bind to Con A‐agarose beads or zona‐intact oocytes and they did not fuse with the zona‐free oocytes. Sperm‐zona binding was also inhibited by UDP‐galactose and UDP‐N‐acetylglucosamine, but not by UDP‐glucose. Sperm motility was not damaged by these inhibitors, and zona‐intact and zona‐free oocytes pretreated with these inhibitors underwent normal fertilization with untreated spermatozoa. These results further strengthen the view that glycoproteins on the sperm surface may be required during different stages of fertilization, including sperm‐egg fusion.