title: Effects of sex hormones on action potential and contraction of guinea pig papillary muscle.
abstract: OBJECTIVE
  To study the effects of sex hormones, estradiol (Est), progesterone (Pro) and testosterone (Tes) on the action potential (AP) and contraction of guinea pig papillary muscle.
  
  
  METHODS
  Using conventional glass microelectrode and mechanical recording of myocardial contraction.
  
  
  RESULTS
  Est slowed down the maximal rate of rise of phase 0 (Vmax) of AP at low concentration (1 mumol.L-1). At 10 mumol.L-1 and above, Est also prolonged AP duration (APD50 and APD90), effective refractory period (ERP) and decreased the maximal isometric tension (Pmax) and velocity of tension development (dT/dt) of contraction. Tes (100 mumol.L-1 - 1 mmol.L-1) prolonged APD90 and ERP with decreased Pmax and dT/dt. But Pro (1 mumol.L-1 - 1 mmol.L-1) had no effects on both AP and contraction.
  
  
  CONCLUSIONS
  Est prolonged AP and depressed contraction of guinea pig papillary muscle.
authors.affiliation: Department of Physiology, Hebei Medical University, Shijiazhuang, China. henryzha@summ.shcnc.ac.cn
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: Y C
authors.initials: YC
authors.lastname: Hao
authors.forename: L L
authors.initials: LL
authors.lastname: Song
authors.forename: S M
authors.initials: SM
authors.lastname: Guo
authors.forename: S Z
authors.initials: SZ
authors.lastname: Gu
authors.forename: S G
authors.initials: SG
authors.lastname: Lu
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003864:Depression, Chemical; D004958:Estradiol / Q000494:pharmacology; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D013739:Testosterone / Q000494:pharmacology
chemical_list: D012739:Gonadal Steroid Hormones; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol