title: Is the preconditioning threshold different in females?
abstract: BACKGROUND
  Preconditioning is injury induced protection against subsequent insult. Studies have shown that both males and females may be preconditioned. Females appear to have an innate cardioprotection, therefore, we hypothesized that the preconditioning threshold may differ between males and females.
  
  
  METHODS
  Male and female rats were divided into five groups (n=4-9). Animals were given an intraperitoneal (i.p.) injection of 125, 250, or 500 micrograms/kilogram Salmonella typhimurium lipopolysaccharide (ETX) or 0.4-ml normal saline (NS). After 24-h incubation another i.p. injection of either 500 micrograms/kilogram ETX (injury dose) or NS was given and the animals incubated an additional 6 h. Shams received two injections of NS. Non-preconditioned rats (PC-) received NS followed by ETX. Preconditioned rats had i.p. injections of 125 mug/kg ETX (PC +125), 250 microg/kg ETX (PC +250), or 500 microg/kg ETX (PC +500) followed by the injury dose ETX. The rats were then anesthetized and myocardial function evaluated with the Langendorff perfusion model.
  
  
  RESULTS
  PC +500 females were preconditioned and were able to maintain cardiac function similar to shams. Conversely, PC +125 females were not preconditioned with this stimulus and had a significant decrease in cardiac function similar to PC- rats. Male PC +500 and PC +125 rats, however, retained cardiac function comparable to shams, while PC- males showed a significant decrement.
  
  
  CONCLUSIONS
  Males and females may each be preconditioned by endotoxin; however, the preconditioning threshold is higher in females than males.
authors.affiliation: Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Pitcher
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Nagy
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: Daniel R
authors.initials: DR
authors.lastname: Meldrum
mesh_terms: D000818:Animals; D004731:Endotoxins / Q000009:adverse effects; D005260:Female; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D017202:Myocardial Ischemia / Q000139:chemically induced / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects*
chemical_list: D004731:Endotoxins