title: Moderate increase of reactive oxygen species triggers meiotic resumption in rat follicular oocytes.
abstract: OBJECTIVE
  The mammalian ovary generates reactive oxygen species (ROS) on an extraordinary scale; however, the role of ROS during meiotic cell cycle progression in follicular oocytes remains poorly understood. The present study was aimed to determine whether a moderate increase of ROS level in the ovary is beneficial for meiotic resumption from diplotene arrest in follicular oocytes.
  
  
  METHODS
  Cumulus oocyte complexes were collected from the ovaries of female rats that had been treated with either: (i) pregnant mare's serum gonadotrophin; or (ii) pregnant mare's serum gonadotrophin + human chorionic gonadotrophin. We analyzed morphological changes, ROS and hydrogen peroxide levels, catalase activity, 3',5'-cyclic adenosine monophosphate and 3',5'-cyclic guanosine monophosphate levels, Thr14/Tyr15, Th-161, total cyclin-dependent kinase 1 (Cdk1) and cyclin B1 levels.
  
  
  RESULTS
  Human chorionic gonadotrophin treatment induced meiotic resumption from diplotene arrest and extrusion of first polar body in cumulus oocyte complexes collected from ovaries and cultured for 3 h in vitro. Meiotic resumption from diplotene arrest was associated with increased ROS and hydrogen peroxide levels but decreased 3',5'-cyclic adenosine monophosphate as well as 3',5'-cyclic guanosine monophosphate levels. The reduced cyclic nucleotide levels were associated with decreased Thr161 phosphorylated Cdk1 and cyclin B1 level but increased Thr14/Tyr15 phosphorylated Cdk1 level leading to maturation promoting factor destabilization. Destabilized maturation-promoting factor triggered meiotic resumption from diplotene arrest and progression to metaphase-I as well as metaphase-II stage in follicular oocytes.
  
  
  CONCLUSIONS
  Our findings suggest that a moderate increase of ROS in the ovary is beneficial for meiotic resumption from diplotene arrest and extrusion of first polar body in follicular oocytes.
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, UP, India.
authors.forename: Meenakshi
authors.initials: M
authors.lastname: Tiwari
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, UP, India.
authors.forename: Shail K
authors.initials: SK
authors.lastname: Chaube
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D054885:Cumulus Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D056744:Cyclin B1 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D005260:Female; D006062:Gonadotropins / Q000494:pharmacology; D006736:Horses; D006801:Humans; D008297:Male; D008540:Meiosis; D049469:Meiotic Prophase I / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: C534701:Ccnb1 protein, rat; D006063:Chorionic Gonadotropin; D056744:Cyclin B1; D006062:Gonadotropins; D017382:Reactive Oxygen Species; D000242:Cyclic AMP; D016203:CDC2 Protein Kinase; C548796:Cdk1 protein, rat; D018844:Cyclin-Dependent Kinases; D006152:Cyclic GMP
keywords: assisted reproductive technology; cumulus oocyte complexes; maturation promoting factor; reactive oxygen species; signal molecules