title: Physiology of meiosis-activating sterol: endogenous formation and mode of action.
abstract: BACKGROUND
  In the context of mammalian oocyte maturation, it has been suggested that intermediates of cholesterol biosynthesis may represent the physiological signal that instructs the oocyte to reinitiate meiosis.
  
  
  METHODS
  Endogenous levels of follicular fluid meiosis-activating sterol (FF-MAS) were monitored in rabbit ovarian tissue, and the influence of exogenous gonadotrophins on sterol formation was assessed. The involvement of cAMP in FF-MAS-induced versus spontaneous oocyte maturation in vitro in mice was also investigated, as was the direct microinjection of FF-MAS into mouse oocytes.
  
  
  RESULTS
  Levels of FF-MAS in rabbit ovaries were significantly elevated 1 h after hCG/LH induction and remained so for 4 and 12 h after induction. In naked oocytes undergoing spontaneous maturation, a significant decrease in cAMP was detected after 30 min of culture. However, FF-MAS-mediated induction of oocyte maturation in hypoxanthine-arrested naked oocytes was not associated with any detectable decrease in intracellular cAMP levels. Microinjected FF-MAS failed to induce any noticeable meiosis.
  
  
  CONCLUSIONS
  A rapid increase in FF-MAS level occurred in vivo in the rabbit ovary in response to LH, and clear differences were seen in the cAMP pattern during spontaneous and induced oocyte maturation in mice.
authors.affiliation: Fertility Team, Research and Development, Novo Nordisk A/S, Copenhagen, Schering AG, Berlin, Germany. chgr@novonordisk.com
authors.forename: Christian
authors.initials: C
authors.lastname: Grøndahl
authors.forename: Jens
authors.initials: J
authors.lastname: Breinholt
authors.forename: Philip
authors.initials: P
authors.lastname: Wahl
authors.forename: Anthony
authors.initials: A
authors.lastname: Murray
authors.forename: Thomas Høst
authors.initials: TH
authors.lastname: Hansen
authors.forename: Inger
authors.initials: I
authors.lastname: Faerge
authors.forename: Carsten E
authors.initials: CE
authors.lastname: Stidsen
authors.forename: Kirsten
authors.initials: K
authors.lastname: Raun
authors.forename: Christa
authors.initials: C
authors.lastname: Hegele-Hartung
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D002782:Cholestenes / Q000008:administration & dosage / Q000378:metabolism*; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D018920:Coculture Techniques; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006801:Humans; D019271:Hypoxanthine / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism; D051379:Mice; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D010053:Ovary / Q000378:metabolism; D011817:Rabbits; D012709:Serum Albumin / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D015398:Signal Transduction
chemical_list: D002782:Cholestenes; D006063:Chorionic Gonadotropin; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; D019271:Hypoxanthine; C100324:4,4-dimethylcholesta-8,14,24-trienol; D007986:Luteinizing Hormone; D000242:Cyclic AMP