title: Rat uterine myometrium contains the gap junction protein connexin45, which has a differing temporal expression pattern from connexin43.
abstract: OBJECTIVE
  Our purpose was to determine whether myometrial cell lines and rat myometrial tissue contained additional gap junction proteins besides connexin43.
  
  
  METHODS
  Syrian hamster myocytes (SHM-ER) and human SK-UT-1 myometrial cell lines were analyzed for intercellular coupling by microinjection of Lucifer yellow. These cell lines and myometrial tissue isolated from pregnant rats were analyzed for connexin expression by ribonucleic acid blotting and immunofluorescence.
  
  
  RESULTS
  SHM-ER and SK-UT-1 cells showed functional gap junctional coupling by intercellular passage of microinjected dye. Both cell lines contained connexin43 and connexin45 messenger ribonucleic acids but did not contain any other detectable connexin messenger ribonucleic acids. Immunofluorescence confirmed the presence of connexin43 and connexin45 proteins in these cells. Connexin 43 and connexin45 messenger ribonucleic acids and immunoreactive proteins were detected in pregnant rat myometrium. Connexin 43 messenger ribonucleic acid levels increased dramatically at term. In contrast, connexin45 messenger ribonucleic acid was present in nonpregnant myometrium, remained relatively constant early in gestation, fell just before term, and more than doubled post partum.
  
  
  CONCLUSIONS
  Rat uterine myometrium contains connexin45 and connexin43. Coexpression of connexin45 with connexin43 in uterine myometrium may regulate gap junctional coupling between these cells. The different temporal expression patterns suggest that connexin45 and connexin43 may have different roles or that the ratio of these connexins may be important in the increased cellular coupling coincident with the onset of labor.
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Albrecht
authors.forename: N S
authors.initials: NS
authors.lastname: Atal
authors.forename: P N
authors.initials: PN
authors.lastname: Tadros
authors.forename: A
authors.initials: A
authors.lastname: Orsino
authors.forename: S J
authors.initials: SJ
authors.lastname: Lye
authors.forename: Y
authors.initials: Y
authors.lastname: Sadovsky
authors.forename: E C
authors.initials: EC
authors.lastname: Beyer
mesh_terms: D000818:Animals; D002460:Cell Line; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D005260:Female; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D006801:Humans; D007546:Isoquinolines; D008647:Mesocricetus; D009215:Myometrium / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D018031:Connexin 43; D017630:Connexins; D005456:Fluorescent Dyes; D007546:Isoquinolines; D012333:RNA, Messenger; C082920:connexin 45; C017475:lucifer yellow