OBJECTIVETo investigate the expression of angiotensin converting enzyme (ACE) and ACE2 Gene in lung of paraquat poisoning rats and the protection of sodium dimercaptopropane sulfonate (Na-DMPS).

METHODSOne hundred SD male rats were randomly equally divided into 4 groups:normal control group (10 rats), drug control group (40 rats), paraquat poisoning group (40 rats) and drug intervention group(40 rats). The paraquat poisoning and drug intervention group rats were injected intraperitoneally by paraquat (20 mg/kg). The rats in drug intervention group rats were protected by intraperitoneal injection with Na-DMPS (200 mg/kg) 15 min before exposure of paraquat. Behavioral changes of the rats and histological changes of lung tissues under light microscope were observed. And the expression of ACE and ACE2 mRNA in lung tissues of rats both in paraquat poisoned group and drug intervention group were measured by RT-PCR at different time of 6 h, 24 h, 3 and 7 d after poisoning.

RESULTSThe poisoning symptoms of shortness of breath, cramps appeared and deteriorated progressively in rats after paraquat exposure and the protection of NA-DMPS could delay and reduce these symptoms significantly. Histological appearance of disorganization of pulmonary capillary and alveolus, exudation in alveolar space, pulmonary edema, severe bleeding, and inflammatory cells infiltration were obvious in lungs of rats after paraquat poisoning, whereas the histological changes were extenuated by protection of NA-DMPS. As compared with normal control group (NC group), the expressions of ACE, ACE2 mRNA in lung tissue decreased, and the lowest level of ACE mRNA expressions appeared at 24 h (0.457 +/- 0.262), on 3 d (0.385 +/- 0.179) after Paraquat exposure (P < 0.05), while lowest level of ACE2 mRNA expressions appeared on 3 d (0.415 +/- 0.247), 7 d (0.365 +/- 0.215) (P < 0.05). As compared with paraquat poisoned group, the expressions of ACE mRNA in lung tissue of rats in NA-DMPS protected group increased significantly at 24 h (0.739 +/- 0.558) and 3 d (0.749 +/- 0.414) (P < 0.05), while the expressions of ACE2 mRNA increased markedly on 3 d (0.584 +/- 0.345) and 7 d (0.493 +/- 0.292) (P < 0.05). But the expression of ACEmRNA and ACE2 mRNA in lungs had no statistical significance between normal control group and drug intervention group (P > 0.05).

CONCLUSIONThe expressions of ACE and ACE2 mRNA in lung tissue of the rats with paraquat poisoning are decreased. Na-DMPS can effectively improve the balance of RAS in local lung tissue and reduce the pathological changes of lung tissue, delay the poisoning symptoms and show protective effects for acute lung injury induced by paraquat.