The inhibitory effects of dexamethasone on inflammatory responses in the lung tissue of rabbits with acute lung injury induced by seawater drowning

Objective To investigate the effect of dexamethasone on inflammatory responses in the lung tissue of rabbits with acute lung injury induced by seawater drowning. Methods Seawater (4 ml/kg body weight) was instilled into the lower trachea of ventilated, anesthetized rabbits. Then 20 minutes later, these rabbits were assigned randomly to receive intravenous injection of 1 mg/kg body weight of dexamethasone (designated as dexamethasone treatment group, DG, n = 12) or 2 ml of normal saline (control group, CG, n = 12). A portion of right lower lung was prepared for light microscopic examination. Expressions of TNF-α, IL-1βand IL-8 mRNA in lung tissue were measured by reverse transcriptase-polymerase chain reaction ( RT-PCR) , and concentrations of proteins were detected by ELISA. Results Light microscopic finding in the CG demonstrated a marked lung injury, represented by hemorrhage, edema, thickened alveolar septum, formation of hyaline membranes and the infiltration of inflammatory cells in alveolar spaces. In the DG, these changes were less pronounced. The DG's TNF-α, IL-1βand IL-8 mRNA and protein were significantly lower than those in the CG. Conclusions Dxamethasone can inhibit the expressions of TNF-α, IL-1βand IL-8, and relieve the inflammatory responses in the lung tissue of rabbits with acute lung injury induced by seawater drowning.