Objective: To investigate the protective efficacy of rabbit endogenous nitric oxide (NO) against acute rabbit lung injury associated with ischemia-reperfusion and explore the possible mechanism.
Methods: The rabbit lung ischemia-reperfusion (LIR) model was established; thirty-two adult New Zealand white rabbits were randomly divided into four groups. The rabbits of control group underwent sham operation. In group LIR, the rabbits' left lung hili were clamped for 60 minutes and then released. In group LIR+L-Arg (L-arginine), the rabbits were operated upon as those in group LIR, but L-Arg (200 mg/kg) was infused into blood circulation as substrate for NO generation before removal of the clip. In group LIR+L-NNA (L-ng-nitro-Arginine), the rabbits passed through the same operation as in group LIR, but L-NNA (10 mg/kg) was infused into circulation as an inhibitor against NO generation before reperfusion. After reperfusion for 60 minutes, the lung tissues were harvested for histological examination, and the wet to dry ratio of lung tissue weight (W/D), myeloperoxidase (MPO) activity, malondialdehyde (MDA) content as well as the ratio of nitrate/nitrite (N/N) were measured respectively.
Results: The group LIR had greater lung tissue W/D, higher MPO activity and MDA content, lower ratio of N/N, and serious pulmonary edema as compared with group ShO (P<0.01). But in group LIR+L-Arg, the degree of pulmonary edema was alleviated, the MPO activity and MDA content were decreased, and the ratio of N/N increased; there was statistically significant difference between group LIR and group LIR+Arg in respect to the above indices (P<0.01). However, in group LIR+L-NNA, the pulmonary edema was even more severe, the MPO activity and MDA content were significantly higher those that in group LIR or group LIR+L-Arg (P<0.01).
Conclusion: The endogenous release of pulmonary NO can attenuate the acute lung injury associated with LIR, and the mechanisms may involve the protective efficacy conferred by endogenous NO against accumulation of neutrophil in lung, against pulmonary microvascular permeability, and against the oxygen free radical injury to lung.