Role of nitric oxide in lung injury associated with experimental acute pancreatitis

This study evaluated the effect of varying the synthesis of nitric oxide with sodium nitroprusside or N‐nitro‐L‐arginine methyl ester (L‐NAME) in a pancreatitis‐lung injury model. Rats (n = 45) were randomized to control or caerulein‐induced pancreatitis groups, treated with saline, sodium nitroprusside (0·4 μg/kg) or L‐NAME (10 mg/kg). Myeloperoxidase activity was used as a measure of neutrophil infiltration. Wet to dry (W:D) lung weight and bronchoalveolar lavage (BAL) protein concentrations were used to assess vascular leakage. Pancreatitis was shown to induce pulmonary neutrophil influx: mean(s.e.m.) myeloperoxidase activity 6·79(0·5) units/g in caerulein‐treated animals versus 2·08(0·5) units/g in controls (P < 0·001). Animals with pancreatitis showed increased microvascular leakage compared with controls (mean(s.e.m.) W:D lung weight 7·01(0·5) versus 2·85(0·2), P < 0·001; BAL protein concentration 2539(222) versus 347(32) μg/ml, P < 0·001). Compared with the saline‐treated pancreatitis group, these changes were reduced by sodium nitroprusside (mean(s.e.m.) myeloperoxidase activity to 2·5(0·4) units/g, P < 0·001; W:D lung weight to 3·8(0·37), P < 0·001; BAL protein concentration 1389(182) μg/ml, P < 0·05). L‐NAME exacerbated the pancreatitis‐induced pulmonary oedema (W:D lung weight increased to 11·96(0·6), P < 0·001), protein leakage (BAL protein concentration rose to 3707(309) μg/ml, P < 0·05) and neutrophil infiltration (myeloperoxidase activity increased to 9·01(0·3) units/g, P < 0·05). These data suggest that, in vivo, nitric oxide inhibits pancreatitis‐induced lung injury, possibly in part by inhibiting pulmonary neutrophil influx.