Human preovulatory oocytes have a higher sperm-binding ability than immature oocytes under hemizona assay conditions: evidence supporting the concept of "zona maturation".
OBJECTIVE
The purpose of this study was to investigate the sperm-binding potential of human oocytes at different stages of nuclear maturation under hemizona assay (HZA) conditions.


METHODS
This was a prospective study designed in a blinded fashion.


METHODS
Academic research environment approved by the Institutional Review Board.


METHODS
Surplus oocytes, donated by patients undergoing in vitro fertilization therapy after gonadotropin stimulation, were analyzed. Semen from a fertile donor was used in all assays.


METHODS
Five groups of oocytes were considered: (1) immature, prophase I; (2) metaphase I; (3) metaphase II; (4) inseminated, unfertilized metaphase II; and (5) immature, prophase I oocytes matured in vitro to metaphase II. Oocytes were stored in salt solution (pH 7.2) and microbisected before assay.


METHODS
Tight binding of sperm to the zona pellucida under HZA conditions was evaluated after 4 hours of gametes coincubation.


RESULTS
Metaphase II oocytes (groups 3 and 4) had significantly higher binding than other groups (P = 0.0001). The mean value of the difference between the two halves (hemizona) was not significant, thus showing a small intra-assay variation for all maturational stages.


CONCLUSIONS
Full meiotic competence of human oocytes is associated with an increased zona pellucida-binding potential.
Oehninger
S
S
Jones Institute for Reproductive Medicine, Department of Obstetrics and Gynecology, Eastern Virginia Medical School, Norfolk 23510.
Veeck
L
L
Franken
D
D
Kruger
T F
TF
Acosta
A A
AA
Hodgen
G D
GD
D004311:Double-Blind Method; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D008597:Menstrual Cycle; D008677:Metaphase; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D011418:Prophase; D011446:Prospective Studies; D013084:Sperm-Ovum Interactions; D015044:Zona Pellucida / Q000502:physiology*