Interaction between cumulus cells and the activity of protein kinase C at different stages of bovine oocyte nuclear maturation

The aim of this study was to evaluate the effect of protein kinase C (PK-C) on the meiotic resumption and progression in bovine oocyte, and to determine if the cumulus cells mediate the PK-C action in the regulation of bovine oocyte nuclear maturation. Cumulus-oocyte complexes (COC) and denuded oocytes (DO), randomly allotted to 6 treatments (T) based on the presence of an activator of PK-C (PMA) (T1 and T2), or a phorbol ester unable to activate PK-C (4alphaPDD-control) (T3 and T4) or a basic culture medium (T5 and T6), were cultivated for 7, 9, 12, 18 and 22 hours. The percentage of germinal vesicle breakdown (GVBD) was higher when the oocytes were cultured with PMA than in the control groups with and without cumulus cells. However, PK-C was dependent of cumulus cells to affect the progression to the stages of metaphase I (MI) and metaphase II (MII) at 12 and 18 hours of culture. At 9 and 22 hours, no difference among groups was detected PK-C accelerates the meiotic resumption independently of the somatic cells but depends on cumulus cells for the progression to the stages of MI and MII.