title: Pre-ovulatory LH/hCG surge decreases C-type natriuretic peptide secretion by ovarian granulosa cells to promote meiotic resumption of pre-ovulatory oocytes.
abstract: BACKGROUND
  In mammalian follicles, oocytes are arrested at the diplotene stage of prophase I until meiotic resumption following the LH surge. Recently, C-type natriuretic peptide (CNP), encoded by natriuretic peptide precursor type C (NPPC) was found to suppress mouse oocyte maturation by promoting cyclic guanosine 5'-monophospate (cGMP) production in cumulus cells. However, regulation of NPPC/CNP expression during the pre-ovulatory period and their regulation by the LH surge have not been investigated.
  
  
  RESULTS
  Based on genome-wide analysis of DNA microarray data sets using samples from periovulatory ovaries, we found increases in NPPC transcripts in granulosa cells during pre-ovulatory follicle growth in mice and a rapid decline induced by the pre-ovulatory LH/hCG stimulation. Treatment of pre-ovulatory animals with hCG decreased ovarian CNP content. In isolated ovarian cells, NPPC mRNA was predominantly expressed in mural granulosa cells exhibiting similar regulation following gonadotrophin treatment. In cultured mouse pre-ovulatory follicles, meiosis resumption in oocytes by hCG treatment was accompanied by decreases in NPPC transcript levels. In cultured mouse cumulus cell-oocyte complexes, CNP treatment inhibited the resumption of meiosis with increases in cGMP levels in both cumulus cells and oocytes. In human ovaries, CNP levels in ovarian follicular fluid were also decreased following treatment of patients with an ovulatory dose of hCG.
  
  
  CONCLUSIONS
  Our findings demonstrate gonadotrophins regulation of NPPC/CNP expression in mouse and human ovaries and confirm the role of CNP as a potent paracrine oocyte maturation inhibitor.
authors.affiliation: Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita 010-8543, Japan. kawamura@yf7.so-net.ne.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kawamura
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Nanami
authors.initials: N
authors.lastname: Kawamura
authors.forename: Seido
authors.initials: S
authors.lastname: Takae
authors.forename: Aya
authors.initials: A
authors.lastname: Okada
authors.forename: Yuta
authors.initials: Y
authors.lastname: Kawagoe
authors.forename: Sabine
authors.initials: S
authors.lastname: Mulders
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Terada
authors.forename: Aaron J W
authors.initials: AJ
authors.lastname: Hsueh
mesh_terms: D000328:Adult; D000818:Animals; D006063:Chorionic Gonadotropin / Q000378:metabolism*; D054885:Cumulus Cells / Q000166:cytology; D005260:Female; D006107:Granulosa Cells / Q000166:cytology*; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism*; D008540:Meiosis; D051379:Mice; D020098:Natriuretic Peptide, C-Type / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D009865:Oocytes / Q000166:cytology*; D006080:Ovarian Follicle / Q000378:metabolism; D010053:Ovary / Q000378:metabolism*; D010060:Ovulation
chemical_list: D006063:Chorionic Gonadotropin; D020098:Natriuretic Peptide, C-Type; D007986:Luteinizing Hormone