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The effect of PD98059 on MAPK regulation in cumulus-enclosed and cumulus-free mouse oocytes

Published online by Cambridge University Press:  14 February 2003

Jaroslav Kalous
Affiliation:
Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Rumburská 899, 277 21 Libečhov, Czech Republic
Michal Kubelka
Affiliation:
Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Rumburská 899, 277 21 Libečhov, Czech Republic
Jan Motlík
Affiliation:
Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Rumburská 899, 277 21 Libečhov, Czech Republic

Abstract

The effect of the p42/44 mitogen-activated kinase (MAPK) inhibitor, PD98059, on MAPK activation and meiosis resumption in mouse oocytes was studied. When germinal vesicle (GV)-stage denuded oocytes (DOs) were cultured continuously in 50 μM PD98059, germinal vesicle breakdown (GVBD) was postponed for 2-3 h. MAPK phosphorylation and activation was delayed as well. However, PD98059 did not impair histone H1 kinase activation. After 14 h of culture there was no significant difference in the rate of DOs reaching metaphase II (MII) arrest in either control or experimental conditions. The effect of PD98059 on MAPK inhibition was further tested in epidermal growth factor (EGF)-treated oocyte–cumulus complexes (OCCs). Exposure of GV-stage OCCs for 5 min to EGF (10 ng/ml) induced a considerable increase in MAPK phosphorylation. After OCCs were further cultured in 50 μM PD98059 a rapid dephosphorylation of MAPK was induced. Already after 1 min of treatment the non-phosphorylated form of MAPK dominated, indicating the high effectivity of PD98059. This result indicates that short EGF/PD98059 treatment of OCCs induced MAPK phosphorylation/dephosphorylation in cumulus cells only. As only a transient delay in MAPK phosphorylation and activation was observed in PD98059-treated DOs we conclude that there is also another PD98059-nonsensitive pathway(s) leading to MAPK activation in mouse oocytes. The data obtained suggest that meiosis resumption in mouse oocytes is somehow influenced by the MEK/MAPK activation pathway.

Type
Research Article
Copyright
2003 Cambridge University Press

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