title: Meiotic resumption in response to luteinizing hormone is independent of a Gi family G protein or calcium in the mouse oocyte.
abstract: The signaling pathway by which luteinizing hormone (LH) acts on the somatic cells of vertebrate ovarian follicles to stimulate meiotic resumption in the oocyte requires a decrease in cAMP in the oocyte, but how cAMP is decreased is unknown. Activation of Gi family G proteins can lower cAMP by inhibiting adenylate cyclase or stimulating a cyclic nucleotide phosphodiesterase, but we show here that inhibition of this class of G proteins by injection of pertussis toxin into follicle-enclosed mouse oocytes does not prevent meiotic resumption in response to LH. Likewise, elevation of Ca2+ can lower cAMP through its action on Ca2+-sensitive adenylate cyclases or phosphodiesterases, but inhibition of a Ca2+ rise by injection of EGTA into follicle-enclosed mouse oocytes does not inhibit the LH response. Thus, neither of these well-known mechanisms of cAMP regulation can account for LH signaling to the oocyte in the mouse ovary.
authors.affiliation: Department of Cell Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06032, USA. lmehlman@neuron.uchc.edu
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Mehlmann
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Kalinowski
authors.forename: Lavinia F
authors.initials: LF
authors.lastname: Ross
authors.forename: Albert F
authors.initials: AF
authors.lastname: Parlow
authors.forename: Erik L
authors.initials: EL
authors.lastname: Hewlett
authors.forename: Laurinda A
authors.initials: LA
authors.lastname: Jaffe
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000037:antagonists & inhibitors / Q000502:physiology*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000502:physiology*; D008540:Meiosis / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D037342:Pertussis Toxin / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D002614:Chelating Agents; D004533:Egtazic Acid; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D037342:Pertussis Toxin; D010727:Phosphoric Diester Hydrolases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium