In this study, we investigated the mechanisms of protein kinase B (PKB) activation and its role in cumulus cells during in vitro meiotic resumption of porcine oocytes. PKB activity in cumulus cells was significantly decreased by 12 h cultivation of cumulus-oocyte complexes (COCs) in basic medium. However, the addition of phosphodiesterase inhibitors, hypoxanthine or 3-isobutyl-1-methylxanthine, maintained the level of PKB activity in cumulus cells at comparable with that in cumulus cells just after collection from their follicles. When COCs were cultured with phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, LY294002, PKB activity was significantly decreased, and both caspase 3 activity and the proportion of apoptotic cells were significantly increased as compared with those in cumulus cells just after collection from their follicles. Moreover, the inhibitory effect of hypoxanthine on spontaneous meiotic resumption was overcome by addition of LY294002. On the other hand, markedly high activity of PKB and high intensity of the phosphorylated PKB band were observed in cumulus cells of COCs which were cultured with FSH. The addition of 20 microM LY294002 to FSH-containing medium induced an apoptosis of cumulus cells, whereas little apoptotic-positive signal was detected in COCs cultured with 5 microM LY294002 and FSH. However, the inhibitory effects of LY294002 on progesterone production by cumulus cells and germinal vesicle breakdown in oocytes reached a maximum at 5 microM. Thus, high activity of the PI 3-kinase-PKB pathway in cumulus cells plays an important role in FSH regulation of cell function. Judging from these results, it is estimated that PI 3-kinase in cumulus cells is required for both the suppression of spontaneous meiotic resumption and the induction of gonadotropin-stimulated meiotic resumption.

This article has been cited by other articles:

				H.-Y. Fan, Z. Liu, N. Cahill, and J. S. Richards Targeted Disruption of Pten in Ovarian Granulosa Cells Enhances Ovulation and Extends the Life Span of Luteal Cells Mol. Endocrinol., September 1, 2008; 22(9): 2128 - 2140. [Abstract] [Full Text] [PDF]

				K. Linher, D. Wu, and J. Li Glial Cell Line-Derived Neurotrophic Factor: An Intraovarian Factor that Enhances Oocyte Developmental Competence in Vitro Endocrinology, September 1, 2007; 148(9): 4292 - 4301. [Abstract] [Full Text] [PDF]

				L. Nemcova, E. Nagyova, M. Petlach, M. Tomanek, and R. Prochazka Molecular Mechanisms of Insulin-Like Growth Factor 1 Promoted Synthesis and Retention of Hyaluronic Acid in Porcine Oocyte-Cumulus Complexes Biol Reprod, June 1, 2007; 76(6): 1016 - 1024. [Abstract] [Full Text] [PDF]

				Y. Yamashita, M. Nishibori, T. Terada, N. Isobe, and M. Shimada Gonadotropin-Induced {Delta}14-Reductase and {Delta}7-Reductase Gene Expression in Cumulus Cells during Meiotic Resumption of Porcine Oocytes Endocrinology, January 1, 2005; 146(1): 186 - 194. [Abstract] [Full Text] [PDF]

				R. Roberts, A. Iatropoulou, D. Ciantar, J. Stark, D. L. Becker, S. Franks, and K. Hardy Follicle-Stimulating Hormone Affects Metaphase I Chromosome Alignment and Increases Aneuploidy in Mouse Oocytes Matured in Vitro Biol Reprod, January 1, 2005; 72(1): 107 - 118. [Abstract] [Full Text] [PDF]

				R. Roberts, J. Stark, A. Iatropoulou, D. L. Becker, S. Franks, and K. Hardy Energy Substrate Metabolism of Mouse Cumulus-Oocyte Complexes: Response to Follicle-Stimulating Hormone Is Mediated by the Phosphatidylinositol 3-Kinase Pathway and Is Associated with Oocyte Maturation Biol Reprod, July 1, 2004; 71(1): 199 - 209. [Abstract] [Full Text] [PDF]