Effects of different doses of lipopolysaccharide on acute lung injury in rats

Objective To investigate the changes of plasma interleukin 4 (IL 4) in rats with acute lung injury (ALI) induced by lipopolysaccharide (LPS) and to explore the relationship between IL 4 and ALI. Methods A total of 120 Wistar rats were randomly divided into 2, 4, 6, and 8 mg/kg groups according to different doses of LPS administration at each observing time point. A control group (NS), receiving saline injection, was also employed. The indexes of respiratory rate, PaO 2, wet weight/dry weight (W/D) of lung lobes, and pathological changes were observed at 1, 2, 4, and 6 h after injury. The plasma IL 4 content was detected by enzyme linked immunosorbant assay. Results ① Various degrees of ALI in rats were induced by different doses of LPS. Acute respiratory distress syndrome (ARDS) was induced under the condition of LPS ≥6 mg/kg. ② LPS could induce increased plasma IL 4 in rats. The peak value of plasma IL 4 in rats increased significantly under the condition of LPS ≥6 mg/kg. Conclusion ① ALI model can be duplicated by injection of LPS. ② LPS ≥6 mg/kg is the critical dosage for ARDS in rats. ③ The obvious increase of plasma IL 4 may be associated with the occurrence of ALI/ARDS.