Cumulus cells secrete a meiosis-inducing substance by stimulation with forskolin and dibutyric cyclic adenosine monophosphate.
The role of the cumulus cells in initiating the resumption of meiosis after exposure to forskolin and dbcAMP was studied in the mouse. The resumption of meiosis was monitored by the percentage of germinal vesicle breakdown (GVBD) and polar body formation (PB). The cumulus-enclosed oocytes (CEO) and denuded oocytes (DO) were cultured with and without hypoxanthine (HX) in the culture medium. Three types of experiments were performed: (1) Effect of forskolin on spontaneous resumption of meiosis, i.e. cultures without HX, and two experiments in which HX is present throughout the culture: (2) Effect of transient exposure to forskolin or dibutyric-cyclic adenosinemonophosphate (dbcAMP) on GVBD prior to continued culture without forskolin or dbcAMP (oocyte priming). (3) Priming of CEO with forskolin for 2 hr, separation of cumulus cells and oocytes, followed by coculture of rejoined cumulus cells and oocytes, or coculture of the cumulus cells and new, unprimed DO. (1) Forskolin inhibited a spontaneous resumption of meiosis in a dose-dependent manner during the first 5 hr of culturing. After 22 hr all controls and CEO resumed meiosis, whereas only half of the DO did. (2) At least 1 hr of priming the CEO with forskolin is needed to induce GVBD and PB formation, but forskolin inhibited the resumption of meiosis when present for 24 hr. Similar results were obtained with a high concentration of dbcAMP. (3) A separation and rejoining of oocytes and cumulus cells after priming induced the resumption of meiosis in a significantly greater number of oocytes than in the control oocytes which were not primed.(ABSTRACT TRUNCATED AT 250 WORDS)
Xia
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Department of Obstetrics and Gynecology, Rigshospitalet, University of Copenhagen, Denmark.
Byskov
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AG
Andersen
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CY
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000494:pharmacology; D008540:Meiosis; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D005576:Colforsin; D003994:Bucladesine; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone