title: Gestational change of K+ channel opener effect is correlated with the expression of uterine KATP channel subunits.
abstract: OBJECTIVE
  We analyzed the gestational changes of pharmacological activity and molecular levels of KATP channels in rat myometrium.
  
  
  METHODS
  Using rat myometrium, the effects of K+ channel openers (KCOs) were examined in an isometric tension study of oxytocin-induced contraction. We also examined the effects of KCOs on the intracellular Ca2+ levels of cultured myometrial cells. The expression of myometrial KATP channels was assessed by RT-PCR and Northern blot analysis.
  
  
  RESULTS
  The effect of KCOs were altered during pregnancy, with a significant increase of their potency at day 18 of pregnancy followed by a decline towards the non-pregnant level at the day of delivery. KCOs suppressed the Ca2+ influx across the cell membrane. The mRNAs encoding each component of myometrial KATP channels, Kir6.1 and SUR2B, exhibited gestational stage-dependent alterations similar to those of the effects of KCOs.
  
  
  CONCLUSIONS
  These findings suggest that KCOs inhibit uterine myometrial contraction more effectively during pregnancy than in the non-pregnant state due to gestation-enhanced expression of KATP channels, implying that KCOs might be useful for preventing premature delivery.
authors.affiliation: Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Sawada
authors.forename: Ken-ichirou
authors.initials: K
authors.lastname: Morishige
authors.forename: Kae
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Keiichi
authors.initials: K
authors.lastname: Tasaka
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Kurachi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Murata
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kurachi
mesh_terms: D000818:Animals; D003981:Diazoxide / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects; D009215:Myometrium / Q000187:drug effects* / Q000378:metabolism; D010121:Oxytocin; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D011247:Pregnancy; D012313:RNA / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014590:Uterine Contraction / Q000187:drug effects*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D015221:Potassium Channels; D014665:Vasodilator Agents; C117780:mitochondrial K(ATP) channel; D010121:Oxytocin; D012313:RNA; D003981:Diazoxide