title: Roscovitine inhibits extrusion of second polar body and induces apoptosis in rat eggs cultured in vitro.
abstract: BACKGROUND
  Inhibition of cyclin-dependent kinases (Cdks) may result in meiotic cell cycle arrest and apoptosis in rat eggs in vitro. We aimed to find out whether roscovitine, a Cdk inhibitor, inhibits extrusion of second polar body (II PB) and induced egg apoptosis in vitro.
  
  
  METHODS
  The metaphase-II (M-II) arrested eggs were collected from oviduct and exposed to various concentrations of roscovitine for 3h in vitro. The morphological changes, phosphorylation status of Cdk1, cyclin B1 level, hydrogen peroxide (H2O2), p53, Bax, Bcl2 and cytochrome c expressions, caspase-3 activity and DNA fragmentation were analyzed.
  
  
  RESULTS
  We showed that the lower concentrations of roscovitine significantly reduced Thr-161 phosphorylated Cdk1 level and inhibited extrusion of II PB. The higher concentrations of roscovitine significantly reduced Thr-161 phosphorylated Cdk1 level but total Cdk as well as cyclin B1 levels remained high. Higher concentrations of roscovitine increased H2O2 level and expressions of p53, Bax and cytochrome c in treated eggs. The increased proapoptotic factors induced capsase-3 activity and thereby DNA fragmentation that finally resulted in cytoplasmic fragmentation, a morphological apoptotic feature.
  
  
  CONCLUSIONS
  Our data suggest that roscovitine inhibited II PB extrusion possibly by reducing Thr-161 phosphorylated Cdk1 level and induced apoptosis through mitochondria-caspase-mediated apoptotic pathway in rat eggs cultured in vitro.
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, India.
authors.forename: Anima
authors.initials: A
authors.lastname: Tripathi
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, India. Electronic address: shailchaubey@gmail.com.
authors.forename: Shail K
authors.initials: SK
authors.lastname: Chaube
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D056744:Cyclin B1 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D045304:Cytochromes c / Q000378:metabolism; D005260:Female; D008677:Metaphase / Q000187:drug effects; D010063:Ovum / Q000187:drug effects*; D010766:Phosphorylation; D059705:Polar Bodies / Q000187:drug effects*; D011687:Purines / Q000494:pharmacology*; D051381:Rats; D000077546:Roscovitine; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494828:Bax protein, rat; C534701:Ccnb1 protein, rat; D056744:Cyclin B1; D011687:Purines; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D000077546:Roscovitine; D045304:Cytochromes c; D018844:Cyclin-Dependent Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3
keywords: Cdk1 phosphorylation; DNA fragmentation; Egg apoptosis; Roscovitine; Second polar body extrusion