265 INHIBITION OF CLASS III PHOSPHATIDYLINOSITOL-3-KINASE, BY 3-METHYLADENINE, REVERSIBLY ARRESTS PORCINE OOCYTES AT GERMINAL VESICLE STAGE

Phosphatidylinositol-3-kinases (PI3K) play pivotal roles in the meiotic progression of oocytes from metaphase I to metaphase II stage. This study evaluated the effect of 3-methyladenine (3MA), a specific inhibitor of Class III PI3K, on the meiotic progression of porcine oocytes. Immature porcine oocytes (n = 4744) retrieved from abattoir-derived oocytes were cultured in the absence or presence (10 mM) of 3MA for 22 h and evaluated for meiotic progression by florescent Hoechst 33342 staining. Data were analysed by chi-square test or ANOVA using SPSS software, and differences at P   0.05) from nontreated control oocytes with respect to their ability to fertilize, cleave (74.1 ± 1.2 v. 72.7 ± 2.8%), and form blastocyst (15.4 ± 1.5 v. 12.7 ± 0.6%) upon IVF or parthenogenetic activation (cleavage rate: 89.8 ± 1.7 v. 84.6 ± 5.1%; blastocyst rate: 44.3 ± 12.4 v. 45.1 ± 7.6%). These data suggest that 3MA reversibly blocks and synchronizes the meiotic progression of porcine oocytes at GV stage without affecting their ooplasmic maturation in terms of post-fertilization/activation in vitro embryonic development. Our data also provide indirect evidence for the likely participation of Class III PI3K in meiotic maturation of porcine oocytes beyond GV stage. This work was supported by grants (Code #200901FHT010305191 and #20070401034017) from BioGreen 21 program of RDA, Republic of Korea.