Changes of nitric oxide in acute lung injury induced by seawater drowning and effect of dexamethasone in rabbits

Objective To observe changes of nitric oxide in acute lung injury induced by seawater drowning in rabbits, and to explore effects of-dexamethasone at different doses on acute pulmonary damage. Methods Acute lung injury model was developed with intratracheal instillation of seawater. Thirty -five healthy New Zealand rabbits were randomly divided into 5 groups (n =7, each group): one group with saline treatment, the control group with intratracheal seawater instillation (2 ml/kg)and the rest 3 groups were treated with dexamethasone at different doses (0.5 mg/kg, 1 mg/kg, 5 mg/kg respectively). Sea water was instilled into the lower trachea 20 minutes after surgery. The anesthetized rabbits were given different doses of dexamethasone through injection into cervical artery. Nitric oxide (NO) levels in serum were measured at 1h, 2 h, 3 h and 6 h after injection of dexamethasone. All the animals were sacrificed 6 hours after injection of dexamethasone. The value of W/D, protein content of bronchoalveolar lavage fluid (BALF), levels of malondialdehyde (MDA), activity of nitric oxide synthase (NOS) and superoxide dismutase (SOD) in pulmonary tissues were determined. Changes in orphological structure of lung tissues were observed with light microscopy. Results Seawater drowning could significantly elevate values of W/D, protein contents in BALF and NO levels in serum, enhance MDA and NOS activity and decline SOD activity. Dexamethasone could alleviate acute lung injury induced by seawater drowning. No significant differences in pathological changes were noted between the examethasone treatment group and the seawater drowning group. Conclusions Experiment showed that seawater drowning could significantly increase NO levels in rabbit serum, and dexamethasone could alleviate lung injury induced by seawater drowning, however, no significant statistical differences were seen between the three groups treated with different doses of dexamethasone. Key words: Seawater drowning;  Acute lung injury;  Nitric oxide;  Nitric oxide synthase;  Malondialdehyde;  Dexamethasone