Phosphatidylinositol 3-Kinase in Cumulus Cells is Responsible for Meiotic Progression from M I to M II Stage in Porcine Follicular Oocytes.

Abstract

Porcine cumulus oocyte complexes (COCs) were cultured in an inhibitor free-medium for 24 h and then some of them were denuded. The COCs and denuded oocytes (DOs) were further cultured for 24 h in the presence of Phosphatidylinositol 3-kinase (PI 3-kinase) specific inhibitors, wortmannin and LY294002. In COCs and DOs, wortmannin (10-8, 10-7 M) and LY294002 (5.0 × 10-5 M) significantly increased the proportion of oocytes arrested at M I and decreased that of oocytes reaching M II. Nevertheless, in DOs the differences between in the presence of the inhibitors and the control in the proportion of oocytes reaching M II substantially diminished as compared to those in the case of COCs. Cumulus cell expansion was significantly suppressed by wortmannin and LY294002. It is concluded that PI 3-kinase in cumulus cells plays a regulatory role in meiotic progression beyond M I and cumulus cell expansion in porcine COCs.