PARENT SESSION
GAMETE BIOLOGY AND GAMETOGENESIS - B

Tuesday, August 3, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(418) STRESSING MOUSE OOCYTES LEADS TO MEIOTIC RESUMPTION.

LaRosa, Cean¹, Downs, Stephen¹, ¹ Marquette University, Milwaukee, WI

ABSTRACT- We have recently shown that mouse oocytes contain the stress-response enzyme, AMP-activated protein kinase (AMPK) and that its activation is associated with meiotic induction (Dev Biol 245:200, 2002). The present study was performed to determine if different cellular stresses can induce germinal vesicle breakdown (GVB) in meiotically arrested mouse oocytes. Immature mice were primed with eCG; two days later oocytes were isolated, divested of cumulus cells, and cultured overnight in medium containing dbcAMP or hypoxanthine (HX) to maintain meiotic arrest. The following stresses were tested for an effect on meiotic resumption: (1) Osmotic Stress. dbcAMP-arrested denuded oocytes (DO) were initially pulsed for 15, 30, 45, or 60 min with either 250 or 500 mM sorbitol and then placed in sorbitol-free medium. 500 mM was most effective, triggering a 27% increase in maturation after a 60 min pulse. (2) Oxidative Stress. When dbcAMP-arrested DO were continuously exposed to increasing concentrations of menadione, meiotic resumption was stimulated in a dose-dependent fashion, with 5 M menadione stimulating 36% of the oocytes to undergo maturation. (3) Metabolic Stress. 10 M arsenite produced a 46% increase in maturation in dbcAMP-arrested DO. 2-deoxy-glucose, on the other hand, was ineffective in dbcAMP-arrested oocytes, but stimulated GVB in 33% of HX-arrested DO. (4) Heat Shock. Exposure of dbcAMP-arrested DO to 42°C for 40 min stimulated over 25% of the oocytes to resume meiosis. (5) Physical Stress. Repeated pipeting of DO with a pasteur pipette induced maturation in 40% of dbcAMP-arrested oocytes. Taken together, these data show that stressing the oocytes by a variety of means leads to meiotic resumption. Future work will focus on how this response relates to intracellular levels of AMP, ATP, and cAMP, as well as the active state of AMPK. Supported by funds from the NIH.

KEY WORDS: meiotic resumption, stress, AMPK