title: Progesterone receptor gene expression in preimplantation pig embryos.
abstract: OBJECTIVE
  It is not known whether progesterone, which plays a key role in establishing and maintaining pregnancy, acts directly on embryos or indirectly through the mother's reproductive tract. Since the physiological effects of progesterone are mediated by progesterone receptors (PR), the expression of PR during the preimplantation stages of pig embryos was determined.
  
  
  METHODS
  Preimplantation pig embryos at different developmental stages were examined using reverse transcription-polymerase chain reaction techniques for the purpose of determining PR gene expression. Immunocytochemistry procedures were used to determine whether PR mRNA is translated into PR protein in preimplantation embryos.
  
  
  RESULTS
  PR mRNA was found in pig embryos at the two-cell stage, but levels started to decline at the four-cell stage; none was detected at the five- to eight-cell stage, nor at any time during the morula and blastocyst stages. Results showed that PR protein was immunostained in pig oocytes and embryos at the 4-cell stage, but that no significant immunostaining occurred during the morula and blastocyst stages.
  
  
  CONCLUSIONS
  These results indicate that the effects of PR on early embryogenesis appear to be indirect, perhaps via PR-regulated growth-promoting factors produced in the maternal reproductive tract.
authors.affiliation: Department of Microbiology, Soochow University, Taipei, Taiwan. cying@mail.scu.edu.tw
authors.forename: C
authors.initials: C
authors.lastname: Ying
authors.forename: Y C
authors.initials: YC
authors.lastname: Yang
authors.forename: W F
authors.initials: WF
authors.lastname: Hong
authors.forename: W T
authors.initials: WT
authors.lastname: Cheng
authors.forename: W L
authors.initials: WL
authors.lastname: Hsu
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D007150:Immunohistochemistry; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis; D011980:Receptors, Progesterone / Q000096:biosynthesis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine
chemical_list: D012333:RNA, Messenger; D011980:Receptors, Progesterone