The effect of lowdose endotoxin on interleukin-1β and tumor necrosis factor-α levels following hemorrhagic shock

Objective:To investigate the effects of lowdose endotoxin challenge on plasma and bronchoalveolar lavage fluid (BALF) tumor necrosis factorα(TNFα),interleukin1β(IL1β) levels in rabbits after hemorrhagic shock followed by resuscitation.Methods:22 New Zealand rabbits were assigned to four groups:hemorrhagic shock group ( n =6),endotoxin (1 μg/kg) group ( n =6),hemorrhagic shock plus endotoxin group ( n =6),and normal controls ( n =4).Hemorrhagic shock was sustained by reducing cardic output (CO) to 40% of baseline for 60 minutes,then resuscitated with shed blood and maintained CO as baseline with Ringer solution for 4 hours.After resuscitation of 60 minutes,1 μg/kg of endotoxin was infused intravenously.Results:Plasma IL1β levels increased in animals during shock period,and returned to normal value after resuscitation.Following infusion of lowdose endotoxin,plasma IL1β levels markedly elevated again at 24 hours,and IL1β levels in BALF were significantly higher compared with the controls.No marked changes in plasma TNFα levels were observed in these groups at any time point,while TNFα levels in BALF were significant higher in hemorrhagic shock plus endotoxin group and endotoxin group compared with control group.In addition,a significant difference in left pulmonary drytowet ratio was found between hemorrhagic shock plus endotoxin group and normal controls (0 17±0 02 vs.0 30±0 03).Conclusions:These data suggest that sustained elevation of IL1β rather than TNFα,induced by lowdose endotoxin challenge following acute hemorrhagic shock,may be of importance to increase the sensitivity of pulmonary vascular permeability.