Gonadotropin-releasing hormone agonists induce meiotic maturation and degeneration of oocytes in the in vitro perfused rabbit ovary

The present study was undertaken to assess the effects of gonadotropin-releasing hormone agonists (GnRH-a, buserelin and leuprolide acetate [LA]) on ovulation, oocyte maturation and degeneration, and steroid and prostaglandin production in the perfused rabbit ovary preparation. Ovulation did not occur in any of ovaries treated with buserelin or LA (10(2) to 10(4) ng/mL) in the absence of gonadotropin. Gonadotropin-releasing hormone agonists were associated with the resumption of meiosis in follicular oocytes in a dose-related manner. Furthermore, the addition of GnRH-a to the perfusate significantly increased the percentage of follicular oocytes that showed evidence of degeneration compared with contralateral untreated or human chorionic gonadotropin-treated controls. Prostaglandin E2 and prostaglandin F2 alpha production by the perfused rabbit ovaries were stimulated significantly by GnRH-a treatment. Exposure to GnRH-a failed to increase either progesterone or estradiol production by the perfused rabbit ovaries. These data demonstrate that GnRH-a act directly in the rabbit ovary to trigger meiotic maturation in oocytes within the follicles, concomitantly increasing oocyte degeneration.