PARENT SESSION
BIOLOGY OF MALE AND FEMALE GAMETES
Harborside C
7:30 AM-10:00 AM

(167) EFFECTS OF MELATONIN ON THE MEIOTIC MATURATION OF MOUSE OOCYTES IN VITRO.

Bae, In-Ha¹, Ahn, Hee-Jin¹, Yoon, Sook-Young¹, ¹ Dept of Biology, Seoul

ABSTRACT- Melatonin, which is secreted by pineal gland play an important role in the regulation of ovarian function in most mammals and also has a role in the protection of cells by removing toxic oxygen free radicals brought about by metabolism. In the present study, effects of melatonin on the mouse oocyte maturation were examined using two different culture conditions provided with 5% or 21% oxygen concentration. Morphologically healthy oocytes with distinct germinal vesicle (GV) were collected. They were then cultured for 17 hour at 37°C, 5% CO₂ and 21% O₂ (95% air) or 5% CO₂, 5% O₂ and 90% N₂. Effects of melatonin were examined at a concentration of 0.0001M, 0.01M or 1.0M. For the prevention of spontaneous maturation of immature oocytes during culture, dibutyryl cyclic AMP (dbcAMP) and/or hypoxanthine were included in the medium. Under 21% oxygen condition, oocytes cultured in the presence of 0.01M melatonin showed a significantly higher maturation rates, in terms of germinal vesicle breakdown (GVBD, 95.0% vs 89.0%) and polar body formation (PB, 88.1% vs. 75.4%), compared to those cultured with 0.0001M or 1.0M melatonin. However, no difference was observed in oocytes cultured under 5% oxygen whether they were treated with melatonin or not. In the presence of 0.01M melatonin, oocytes either cultured under 21% or 5% oxygen exhibited no difference in the PB (85.6% vs 86.7%). However, in the absence of melatonin, oocytes cultured under 21% oxygen showed lower PB (74.7%). When oocytes were cultured in the presence of dbcAMP alone or with varying concentrations of melatonin, those treated with both compounds always showed better maturation, compared to those cultured with dbcAMP alone. At the same concentration of melatonin, however, oocytes exposed to 21% oxygen showed poor maturation than those to 5% oxygen. Similar results were obtained from the experiments using hypoxanthine instead of dbcAMP. Based upon these results, it is suggested that melatonin could enhance the meiotic maturation of mouse oocytes under 21% oxygen concentration, and release oocytes from the meiotic arrest by dbcAMP or hypoxanthine regardless of the concentration of oxygen, probably via the removal of oxygen free radicals.

KEY WORDS: Melatonin, Mouse oocyte maturation, Oxygen free radical