CHARACTERISTICS OF AN OVIDUCTAL GLYCOPROTEIN AND ITS POTENTIAL ROLE IN FERTILITY-CONTROL

At the time of ovulation the lining epithelium of the mammalian oviduc t consists of columnar ciliated and secretory cells. These mature cell s are dependent on ovarian steroids in carnivores. Oestradiol induces differentiation of these cells and maintains their mature functional s tate, and progesterone induces dedifferentiation. The secretory cells synthesize and secrete an oestrogen-dependent high molecular weight gl ycoprotein. The cDNAs encoding oviductal glycoproteins from several sp ecies have been sequenced and show high similarity. The human cDNA hyb ridized with a single message on northern blots of total oviduct RNA o btained from oestradiol-treated cats (about 2.3 kb) and dogs (about 2. 1 kb). This glycoprotein is the major nonserum protein present in the oviductal lumen at the time of ovulation, fertilization and early embr yonic development. The glycoproteins associate with the zona pellucida of oviductal eggs in all species studied to date. Recent studies sugg est that the bovine glycoprotein facilitates sperm capacitation and si gnificantly increases the ability of bovine spermatozoa to fertilize b ovine oocytes in vitro, that the hamster glycoprotein increases the sp erm penetration rate of the zona pellucida by three times and that the human glycoprotein increases sperm binding to the zona pellucida by t hree times. All of the evidence for a biological function for this gly coprotein is derived from studies performed in several different speci es at reproductive stages before fertilization. The biological actions of this glycoprotein suggest a potential role for the glycoprotein in fertility control. Specifically, purified or recombinant glycoprotein may improve success in IVF procedures by enhancing binding of spermat ozoa to the zona pellucida and improving fertilization rates. The glyc oprotein may also be a potential immunocontraceptive target since anti bodies generated against the oviductal glycoprotein may prevent fertil ization by preventing binding of spermatozoa to the zona pellucida.