The effect of timing of pneumoperitoneum on the inflammatory response

Background: We examined the effects of an identical period of pneumoperitoneum applied at three different time points after lipopolysaccharide (LPS) challenge. Two different insufflation gases were also compared. Methods: Male rats (n = 70) were injected intravenously with 1 mg/kg of LPS (time 0). The time relationship between a 1.5-h period of insufflation and initial LPS stimulation was the experimental variable. All rats were killed 6 h after injection. CO2 and helium insufflation were investigated. Ten control rats received LPS only. Serum interleukin-6 (IL-6) levels were determined by enzyme-linked immunosorbent assay (ELISA). Hepatic expression of alpha(2)-macroglobulin, beta-fibrinogen, and metallothionein were measured by Northern blot analysis. Statistical analysis was performed using one-way analysis of variance (ANOVA). Results: Expression of alpha(2)-macroglobulin mRNA was lower in CO2 groups compared to the control group) < 0.05 at time 120 and 270). β-Fibrinogen message was diminished in CO2 0 and 120 groups compared to control. Serum levels of IL-6 and expression of metallothionein mRNA did not show significant differences between groups. Conclusions: These findings suggest that CO2 pneumoperitoneum downregulates the inflammatory response to LPS challenge. Start time of CO2, insufflation does not appear to alter hepatic expression of acute phase genes. The mechanism of α(2)-macroglobulin downregulation does not appear to be due to IL-6.