Objective: To investigate the role of angiotensin II as a mediator of burn- and sepsis-induced gut ischemia and reperfusion injury and to determine whether treatment with the angiotensin II inhibitor DuP753 can attenuate mucosal injury and bacterial translocation in a burn/endotoxemia porcine model.
Summary background data: Thermal injuries and endotoxemia have been shown to induce ischemia and reperfusion injury to the intestine, leading to increased mucosal permeability and bacterial translocation. Angiotensin II, the production of which has been reported to increase after burn, is thought to be one of the primary mediators of postburn mesenteric vasoconstriction.
Methods: An ultrasonic flow probe was inserted into the superior mesenteric artery and a catheter into the superior mesenteric vein in 21 female pigs. After 5 days, all animals were anesthetized, and 14 received 40% total body surface area third-degree burn. DuP753 was administered intravenously at 1 microg/kg to seven pigs immediately after burn. Eighteen hours after burn, 100 microg/kg Escherichia coli lipopolysaccharide (LPS) was intravenously administered. Systemic and splanchnic hemodynamics were measured and blood samples were drawn for blood gas analysis. Plasma conjugated dienes (PCDs), an index of lipid peroxidation, were measured every 6 hours. Intestinal permeability was assessed every 6 hours by measuring the lactulose/mannitol excretion ratio. At the end of the study (42 hours), tissue samples were harvested for bacteriologic cultures.
Results: Burn caused a significant decrease in mesenteric blood flow, to approximately 58% of baseline. Postburn endotoxemia significantly reduced the blood flow in the superior mesenteric artery to 53% of baseline. Treatment with DuP753 prevented postburn vasoconstriction and subsequently abrogated the impact of postburn endotoxemia on blood flow in the superior mesenteric artery. Mesenteric oxygen supply was significantly reduced after burn and endotoxin to 60% and 51% of baseline levels, respectively. DuP753 administration significantly improved mesenteric oxygen supply after both insults. Burn- and LPS-induced mesenteric hypoxia, as indicated by decreased mesenteric oxygen consumption, was also ameliorated by DuP753 treatment. PCD levels were significantly elevated 8 hours after burn. LPS caused a higher and prolonged increase in PCD levels. Treatment with DuP753 significantly reduced PCD levels after burn and after LPS. Intestinal permeability, as assessed by the lactulose/mannitol ratio, showed 6-fold and 12-fold increases after thermal injury and LPS, respectively. In contrast, the lactulose/mannitol ratio was only doubled in DuP753-treated animals. Bacterial translocation was significantly increased after burn and endotoxin. The incidence of bacterial translocation in the DuP753-treated animals was similar to that in the sham group.
Conclusions: Angiotensin II appears to play a pivotal role in the burn- and endotoxin-induced intestinal ischemia and reperfusion injury, with subsequent increases in permeability and bacterial translocation. Postburn administration of the angiotensin II receptor antagonist DuP753 significantly reduces the extent of these events.