Treatment with the MAPK kinase inhibitor U0126 during the first two hours of in vitro maturation improves bovine oocyte developmental competence

This study examined the effects of treatment with U0126, which inhibits MAPK by inhibiting MAPK kinase, during the first 2 hr of in vitro maturation on bovine developmental competence and on gap junction (GAPJ) communication between the oocyte and cumulus cells. The percentage of oocytes developing to the blastocyst stage in the group treated with 5 mu M U0126 (28%) was significantly higher than that in controls (15%, p <.05), while that in the group treated with 10 mu M U0126 (18%) was not. Breakdown of the GAPJs was delayed in the group treated with 5 mu M U0126 when compared to controls, as estimated by immunohistochemical examination of connexin 43, which is a primary constituent of the GAPJs. These results indicate that treatment with 5 mu M U0126 during in vitro maturation delays GAPJ breakdown and improves bovine oocyte developmental competence.