title: The role of 17-beta estradiol in ischemic preconditioning protection of the heart.
abstract: BACKGROUND
  The protective effects of 17-beta estradiol (E2) on cardiac tissue during ischemia/reperfusion (I/R) injury have not yet been fully elucidated.
  
  
  OBJECTIVE
  To assess the protective effects of short- and long-term E2 treatments on cardiac tissue exposed to I/R, and to assess the effects of these treatments in combination with ischemic preconditioning (IPC) on cardiac protection from I/R injury.
  
  
  METHODS
  SPRAGUE DAWLEY RATS WERE ASSIGNED TO THE FOLLOWING TREATMENT PROTOCOLS: control (no preconditioning); IPC (isolated hearts were subjected to two cycles of 5 min global ischemia followed by 10 min of reperfusion); E2 preconditioning (E2PC; isolated hearts were subjected to E2 pharmacological perfusion for 15 min); short-term in vivo E2 pretreatment for 3 h; long-term in vivo E2 pretreatment or withdrawal (ovariectomy followed by a six-week treatment with E2 or a placebo); combined IPC and E2PC; combined IPC and short- or long-term E2 pretreatments or withdrawal. All hearts were isolated and stabilized for at least 30 min before being subjected to 40 min of global ischemia followed by 30 min of reperfusion; left ventricular function and vascular hemodynamics were then assessed.
  
  
  RESULTS
  IPC, E2PC and short-term E2 pretreatment led to the recovery of left ventricle function and vascular hemodynamics. Long-term E2 and placebo treatments did not result in any protection compared with untreated controls. The combination of E2PC or short-term E2 treatments with IPC did not block the IPC protection or result in any additional protection to the heart. Long-term E2 treatment blocked IPC protection; however, placebo treatment did not.
  
  
  CONCLUSIONS
  Short-term treatment with E2 protected the heart against I/R injury through a pathway involving the regulation of tumour necrosis factor-alpha. The combination of short-term E2 treatment with IPC did not provide additional protection to the heart. Short-term E2 treatment may be a suitable alternative for classical estrogen replacement therapy.
authors.affiliation: Department of Physiology;
authors.forename: Fawzi A
authors.initials: FA
authors.lastname: Babiker
authors.forename: Lamia J
authors.initials: LJ
authors.lastname: Hoteit
authors.forename: Shaji
authors.initials: S
authors.lastname: Joseph
authors.forename: Abu Salim
authors.initials: AS
authors.lastname: Mustafa
authors.forename: Jasbir S
authors.initials: JS
authors.lastname: Juggi
keywords: Estrogen; Ischemia; Preconditioning; Reperfusion; Tumour necrosis factor-alpha