title: Mu opioid receptor in the human endometrium: dynamics of its expression and localization during the menstrual cycle.
abstract: OBJECTIVE
  To study the dynamics of the expression and localization of the mu opioid receptor (MOR) in human endometrium throughout the menstrual cycle.
  
  
  METHODS
  Analysis of human endometrial samples from different menstrual cycle phases (menstrual, early/midproliferative, late proliferative/early secretory, midsecretory, and late secretory) by reverse transcription-polymerase chain reaction, Western blot, and immunohistochemistry.
  
  
  METHODS
  Academic research laboratory.
  
  
  METHODS
  Women from the Human Reproduction Unit of the Cruces University Hospital, fulfilling the following criteria: normal uterine vaginal ultrasound; absence of endometriosis, polycystic ovary syndrome, implantation failure, or recurrent miscarriage; and no history of opioid drug use.
  
  
  METHODS
  Endometrial samples of 86 women categorized into groups for the menstrual cycle phases: 12 menstrual, 21 early/midproliferative, 16 late proliferative/early secretory, 17 midsecretory, and 20 late secretory.
  
  
  METHODS
  MOR gene and protein expression and localization in the different compartments of the human endometrium at different stages of the menstrual cycle.
  
  
  RESULTS
  The expression of MOR mRNA and protein changed throughout the cycle in human endometrium. MOR expression increased during the proliferative phase and decreased during the secretory one. Lower values were found at menstruation, and maximum values around the time of ovulation. Small variations for each endometrial compartment were found.
  
  
  CONCLUSIONS
  The presence of MOR in human endometrium and the dynamic changes during the menstrual cycle suggest a possible role for opioids in reproduction events related to the human endometrium or endometriosis.
authors.affiliation: Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Bizkaia, Spain.
authors.forename: Lide
authors.initials: L
authors.lastname: Totorikaguena
authors.affiliation: Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Bizkaia, Spain.
authors.forename: Estibaliz
authors.initials: E
authors.lastname: Olabarrieta
authors.affiliation: Human Reproduction Unit, Cruces University Hospital, Biocruces, University of the Basque Country (UPV/EHU), Bizkaia, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Matorras
authors.affiliation: Department of Cell Biology and Histology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Bizkaia, Spain.
authors.forename: Edurne
authors.initials: E
authors.lastname: Alonso
authors.affiliation: Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Bizkaia, Spain.
authors.forename: Ekaitz
authors.initials: E
authors.lastname: Agirregoitia
authors.affiliation: Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Bizkaia, Spain. Electronic address: naiara.aguirregoitia@ehu.eus.
authors.forename: Naiara
authors.initials: N
authors.lastname: Agirregoitia
mesh_terms: D000328:Adult; D015153:Blotting, Western; D004717:Endometrium / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006785:Hospitals, University; D006801:Humans; D007150:Immunohistochemistry; D008597:Menstrual Cycle / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult
chemical_list: C485764:OPRM1 protein, human; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu
keywords: MOR; Mu opioid receptor; endometrium; menstrual cycle