title: An inhibitor of type-1 cyclo-oxygenase in tissues from human pregnancy.
abstract: BACKGROUND
  Previous work has shown that first trimester human decidua contains a protein which directly inhibits the activity of type-1 cyclo-oxygenase (COX-1).
  
  
  METHODS
  Activity assays for cyclo-oxygenase types I and II were developed. Cell cytosol was prepared from a number of different sources: human placenta and decidua (first and third trimester), two placental cell-lines (BeWo and TCL-1), an endometrial stromal cell-line and K562 erythroleukemia cells. The effects of all cytosols on activity of type I cyclo-oxygenase, and of cytosols from BeWo choriocarcinoma and decidual cells on type II enzyme, were tested.
  
  
  RESULTS
  Cytosols from first trimester human placenta, two placental cell-lines, an endometrial stromal cell-line and K562 erythroleukemia cells all inhibited the type I enzyme. The inhibitor protein could not be detected in third trimester human decidual cells after labor, and was present only at very low levels in third trimester decidua prior to the onset of labor. Cytosols from BeWo and decidual cells had no effect on the activity of the type-2 cyclo-oxygenase enzyme.
  
  
  CONCLUSIONS
  The inhibitor of type I cyclo-oxygenase was not specific to pregnancy-related tissues, and may be a general regulator of this enzyme. Lower levels of inhibitor were present at term, but the physiological significance of this is unclear. The cytosolic inhibitor appears to be specific to the type I enzyme.
mesh_terms: D002460:Cell Line; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000032:analysis*; D003600:Cytosol / Q000737:chemistry; D003656:Decidua / Q000737:chemistry*; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008565:Membrane Proteins; D010920:Placenta / Q000737:chemistry*; D049590:Postpartum Period; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011263:Pregnancy Trimester, Third; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*