title: Sexual dimorphism in myocardial tumor necrosis factor-alpha and cardiac function during endotoxin tolerance.
abstract: BACKGROUND
  Preconditioning is injury-induced protection against subsequent injury and may be induced by a variety of stimuli. Both males and females may be preconditioned; however, if females are relatively protected against the initial insult, is their preconditioning threshold higher? We hypothesized that preconditioning injury threshold differences may exist between genders, which may be associated with differences in myocardial inflammatory monokine production.
  
  
  METHODS
  Male and female Sprague-Dawley rats (n=3-5/group) were given intraperitoneal injections of 125 or 500 microg/kg Salmonella typhimurium lipopolysaccharide (ETX) or 0.4 mL normal saline (NS; 154 mmol/L NaCl). After 24 hours, another injection of 500 microg/kg ETX (injury dose) or NS was given, and the animals were incubated an additional 1 or 6 hours. The rats were anesthetized and myocardial function evaluated via the Langendorff perfusion model. Tumor necrosis factor-alpha (TNF-alpha), interleukin-(IL)-1beta, and IL-6 were measured in 1-hour animals via an enzyme-linked immunosorbent assay. Nonpreconditioned rats (PC-) received NS followed by ETX. Preconditioned rats received either 125 microg/kg ETX (PC+125) or 500 microg/kg ETX (PC+500) followed by injury dose ETX.
  
  
  RESULTS
  PC+125 and PC+500 males, as well as PC+500 females, were preconditioned and retained cardiac function similar to shams. PC+125 females were not preconditioned with this stimulus and had a decrease in cardiac function similar to PC- rats. Furthermore, PC+125 and PC+500 males, and PC+500 females had decreased release of TNF-alpha after preconditioning, while PC- animals and PC+125 females did not.
  
  
  CONCLUSIONS
  Males and females can be preconditioned by endotoxin; however the preconditioning threshold is higher in females than males.
authors.affiliation: Department of Surgery, Indiana Center for Vascular Biology and Medicine, Indiana University School of Medicine, Indianapolis, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Pitcher
authors.forename: Ben M
authors.initials: BM
authors.lastname: Tsai
authors.forename: Meijing
authors.initials: M
authors.lastname: Wang
authors.forename: Ajay
authors.initials: A
authors.lastname: Kher
authors.forename: John W
authors.initials: JW
authors.lastname: Brown
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Meldrum
mesh_terms: D000818:Animals; D005260:Female; D007375:Interleukin-1 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D017725:Ventricular Pressure
chemical_list: D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha