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. Materials and 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 mu g/kg ETX (PC + 125), 250 mu g/kg ETX (PC + 250), or 500 mu g/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 PG males showed a significant decrement. Conclusions. Males and females may each be precon ditioned by endotoxin; however, the preconditioning threshold is higher in females than males. (c) 2005 Elsevier Inc. All rights reserved.