title: Embryonic platelet-activating factor: temporal expression of the ligand and receptor.
abstract: OBJECTIVE
  Preimplantation embryos synthesize platelet-activating factor (PAF) and this embryo-derived PAF is required for development. PAF's signal transduction is receptor-mediated and PAF-receptor mRNA is present in early embryos. The study objective was to determine the relationship between PAF production and PAF-receptor mRNA expression levels in mouse preimplantation embryos.
  
  
  METHODS
  Embryo-derived PAF levels were determined by radioimmunoassay. Embryonic PAF-receptor mRNA levels were determined by semiquantitated reverse transcription-polymerase chain reaction.
  
  
  RESULTS
  Embryonic-PAF increased as time progressed at a relatively constant rate (1.4-1.9 x) except between the eight- and morula-cell stages where levels increased sevenfold. Embryonic PAF-receptor expression was highest at the two-cell stage and decreased steadily until the morula stage before increasing again. Regression analysis of embryo-derived PAF on PAF-receptor expression does not demonstrate a significant relationship.
  
  
  CONCLUSIONS
  PAF-receptor expression (mRNA) levels decrease, while embryo-derived PAF levels decrease, as the preimplantation embryo develops. Embryonic-PAF and PAF-receptor mRNA expression do not appear related. Therefore, embryonic-PAF does not appear to regulate expression of its own receptor in vitro. The data provide a clue to the complicated cell signaling system involving PAF production and receptor expression that may help our understanding of developmental events.
authors.affiliation: Reproductive Biology Associates, Atlanta, Georgia 30342, USA. roudebush@mindspring.com
authors.forename: William E
authors.initials: WE
authors.lastname: Roudebush
authors.forename: Elissa T
authors.initials: ET
authors.lastname: Purnell
authors.forename: Neil R
authors.initials: NR
authors.lastname: Stoddart
authors.forename: Steven D
authors.initials: SD
authors.lastname: Fleming
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D047108:Embryonic Development; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D010972:Platelet Activating Factor / Q000235:genetics / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled
chemical_list: D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor