Experimental extension of the time interval between oocyte maturation and ovulation: effect on fertilization and first cleavage.
OBJECTIVE
To test the hypothesis that impaired fertility in human patients with high LH concentrations throughout the follicular phase of the menstrual cycle reflects premature maturation of their oocytes.


METHODS
Previous information that resumption of meiosis is induced by lower hCG concentrations than that required for stimulation of follicular rupture was confirmed and used for establishment of a rat animal model in which oocyte maturation and ovulation can be separated experimentally. In further experiments hypophysectomized, pregnant mare serum gonadotropin (PMSG)-primed, immature female rats injected with 1.1 IU of hCG, a dose found to induce maturation in 72.9% +/- 6% of the rats with no effect on ovulation, were administered with a second injection of an ovulatory dose (4 IU) of hCG, 24 hours later. The ovulated eggs were subjected to IVF.


RESULTS
Fertilization and first cleavage in oocytes recovered from our experimental animal model were similar to that observed in control PMSG-primed, either hypophysectomized or intact rats, treated by a single injection of 4 IU of hCG.


CONCLUSIONS
The extension of the time interval between oocyte maturation and ovulation in the rat does not result in a lower rate of fertilization or a reduced incidence of cleavage. However, an inferior developmental capacity of these embryos cannot be ruled out.
Dekel
N
N
Department of Hormone Research, Weizmann Institute of Science, Rehovot, Israel.
Ayalon
D
D
Lewysohn
O
O
Nevo
N
N
Kaplan-Kraicer
R
R
Shalgi
R
R
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005300:Fertility Agents, Female / Q000494:pharmacology; D005306:Fertilization / Q000502:physiology*; D005498:Follicular Phase / Q000097:blood / Q000187:drug effects / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood; D009865:Oocytes / Q000166:cytology* / Q000502:physiology*; D010060:Ovulation / Q000502:physiology*; D010062:Ovulation Induction; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D015053:Zygote / Q000166:cytology / Q000502:physiology
D006063:Chorionic Gonadotropin; D005300:Fertility Agents, Female; D007986:Luteinizing Hormone