title: Signaling pathways in ascidian oocyte maturation: the role of cyclic AMP and follicle cells in germinal vesicle breakdown.
abstract: Many ascidian oocytes undergo 'spontaneous' germinal vesicle breakdown (GVBD) when transferred from the ovary to normal pH 8.2 sea water (SW); however, low pH inhibits GVBD, which can then be stimulated while remaining in the low pH SW. Oocytes of Boltenia villosa blocked from GVBD by pH 4 SW undergo GVBD in response to permeant cyclic AMP (8-bromo-cyclic AMP), phosphodiesterase inhibitors (isobutylmethylxanthine and theophylline) or the adenylyl cyclase activator forskolin. This suggests that cAMP increases during GVBD. Removal of the follicle cells or addition of a protease inhibitor inhibits GVBD in response to raised pH but not to forskolin, theophylline or 8 bromo-cAMP. Isolated follicle cells in low pH SW release protease activity in response to an increase in pH. These studies imply that the follicle cells release protease activity, which either itself stimulates an increase in oocyte cAMP level or reacts with other molecules to stimulate this process. Studies with the mitogen-activated protein (MAP) kinase inhibitors U0126 and CI 1040 suggest that MAP kinase is not involved in GVBD. The Cdc25 inhibitor NSC 95397 inhibits GVBD at 200 nm in a reversible manner.
authors.affiliation: University of Washington Friday Harbor Laboratories, 620 University Road, Friday Harbor, WA 98250, USA. clambert@fullerton.edu
authors.forename: Charles C
authors.initials: CC
authors.lastname: Lambert
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002467:Cell Nucleus / Q000502:physiology* / Q000648:ultrastructure; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D008540:Meiosis / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D009866:Oogenesis / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012623:Seawater; D015290:Second Messenger Systems / Q000502:physiology*; D014561:Urochordata / Q000502:physiology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D047428:Protein Kinase Inhibitors; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases