title: Sperm entry into zona-free oocytes in the hamster oviduct: implications for the mechanisms of acrosome reaction induction.
abstract: The possible importance of the zona pellucida for induction of the acrosome reaction (AR) and establishment of sperm/egg associations in the fallopian tube was investigated by instilling zona-free eggs into the oviductal ampulla of hamsters that had been inseminated with epididymal spermatozoa 6-7 hours previously. The eggs were recovered only 60-90 minutes later because of increasing difficulty with time of collecting zona-free eggs from the oviduct. In the zona-free group, 41 (4%) of 1,101 transferred eggs were recovered, of which 20% contained spermatozoa with decondensing nuclei (mean 4.4/egg). A similar (22%) fertilization rate (mean 3.2 spermatozoa/egg) was found among intact (control) eggs recovered after instillation into the contralateral oviduct. Mammalian spermatozoa are not incorporated even into zona-free eggs before AR occurs. These results thus demonstrate that an AR in functional hamster spermatozoa in vivo and establishment of sperm/egg associations in vivo require no interaction with the zona pellucida nor with other products of ovulation.
authors.affiliation: Department of Obstetrics and Gynecology, Cornell University Medical College, New York, New York 10021.
authors.forename: P S
authors.initials: PS
authors.lastname: Cuasnicu
authors.forename: J M
authors.initials: JM
authors.lastname: Bedford
mesh_terms: D000177:Acrosome / Q000502:physiology*; D000818:Animals; D006224:Cricetinae; D010064:Embryo Implantation; D005260:Female; D005306:Fertilization; D007315:Insemination, Artificial; D008297:Male; D008647:Mesocricetus; D010063:Ovum / Q000502:physiology*; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*; D015044:Zona Pellucida / Q000502:physiology*