Is the preconditioning threshold different in females?
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.
Pitcher
Jeffrey M
JM
Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Nagy
Ryan D
RD
Tsai
Ben M
BM
Wang
Meijing
M
Kher
Ajay
A
Meldrum
Daniel R
DR
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*
D004731:Endotoxins