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Background Mortality after acute respiratory distress syndrome is higher in males than in females. Gender differences in pulmonary vascular reactivity and local inflammatory response may explain this disparity. We hypothesized that endothelium-dependent pulmonary vasorelaxation is impaired in males and that this effect is related to differences in local inflammatory cytokine expression from the pulmonary vasculature. Methods Pulmonary artery (PA) rings (n = 12-16 per group) were isolated from adult male and female Sprague-Dawley rats treated with endotoxin (Salmonella typhimurium lipopolysaccharide, 20 mg/kg IP) or vehicle (0.9% normal saline), and connected to force transducers for measurement of isometric force displacement. Dose-response curves (0.01-10 μmol/L) to the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator sodium nitroprusside were generated. PA rings were also evaluated for inducible nitric oxide synthase, tumor necrosis factor-alpha, and interleukin 1β messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction. Results Endotoxin had no effect on the maximum PA contraction in males (564.4 ± 37.37 mg vs 633.3 ± 54.67 mg vehicle) or females (446.3 ± 20.00 mg vs 444.2 ± 33.02 mg vehicle), but endothelium-dependent vasodilation was significantly decreased in males (47.49 ± 5.63% vs 77.61 ± 9.41% vehicle). Endothelium-independent vasodilation remained intact during endotoxemia. Endotoxin increased the PA expression of inducible nitric oxide synthase mRNA, but there was no gender difference. There was no change in expression of PA tumor necrosis factor, whereas endotoxemic males, but not females, had increased interleukin 1β mRNA, compared with vehicle. Conclusions These results suggest that sepsis-induced vascular dysfunction differs between males and females, and, therefore, treatment of acute lung injury may require gender-specific therapies.

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 μg/kg Salmonella typhimurium lipopolysaccharide (ETX) or 0.4 mL normal saline (NS; 154 mmol/L NaCl). After 24 hours, another injection of 500 μg/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-α (TNF-α), interleukin-(IL)-1β, 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 μg/kg ETX (PC+125) or 500 μg/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-α 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.