褪黑激素对严重烧伤大鼠急性肺损伤的保护作用

Protective effect of melatonin against acute lung injury in severely-burned rats

目的:观察褪黑激素对烧伤大鼠肺组织氧化应激损伤和肺水肿的保护作用。方法:实验于2005-03/11在青岛大学医学院完成。选用30只SD大鼠,随机分为对照组、烧伤组和褪黑激素组3组,每组10只。烧伤组和褪黑激素组大鼠麻醉后将背部皮肤置于沸水中15s造成30%Ⅲ度烫伤,伤后立即腹腔注射溶剂(体积分数为0.01的乙醇生理盐水)或褪黑激素10mg/kg,30min后腹腔注射15mL生理盐水复苏。对照组除背部浸入37℃水中且未补液外,其余同烧伤组。所有动物均于伤后6h断头处死,取出双肺测量以下指标:丙二醛和还原型谷胱甘肽含量,谷胱甘肽过氧化物酶、超氧化物歧化酶和髓过氧化物酶活性,以及肺质量(湿)/肺质量(干)比值。结果:30只大鼠全部进入结果分析。①丙二醛含量:烧伤组显著高于对照组和褪黑激素组[(2.02±0.52),(1.39±0.36),(1.11±0.29)μmol/g,P<0.01],对照组和褪黑激素组间差异不显著。②还原型谷胱甘肽含量:烧伤组显著低于对照组和褪黑激素组[(7.42±1.01),(12.67±1.68),(11.18±1.63)μmol/g,P<0.01],褪黑激素组仍低于对照组(P<0.05)。③烧伤组谷胱甘肽过氧化物酶和超氧化物歧化酶活性均低于对照组(P<0.001,P<0.01),而髓过氧化物酶活性比对照组高5.4倍(P<0.001)。褪黑激素组谷胱甘肽过氧化物酶活性高于烧伤组(P<0.01),髓过氧化物酶水平比烧伤组低21%(P<0.05)。④肺质量(湿)/肺质量(干)比值:烧伤组显著高于对照组和褪黑激素组(4.42±0.51,3.57±0.64,3.98±0.15,P<0.01,0.05),对照组和褪黑激素组间差异不显著。结论:褪黑激素可明显抑制烧伤后肺组织氧化应激损伤和肺水肿,对烧伤早期急性肺损伤具有一定的保护作用。

AIM： To observe the protective effect of melatonin （MLT） on the oxidative stress injury and pulmonary oedema of lung tissues in severelyburned rats. METHODS： The experiment was conducted at the Medical College of Qingdao University between March and November 2005. Totally 30 SD rats were randomly assigned to 3 groups with 10 in each： control group, burh group and MLT group. The 30% full-thickness bums were induced under anesthesia by immersing the dorsal skin into boiling water for 15 seconds in the rats of bum group and MLT group, which were given the intraperitoneal （ip） injection of 0.01 ethanol saline or 10 mg/kg MLT immediately postbum, and resuscitated with 15 mL saline ip 30 minutes later. The control rats were treated identically as those of bum group except for immersion to 37 ℃ water without fluid replacement. All the animals were decapitated at 6 hours postbum, and then the lungs were collected for different measurements： malondialdehyde （MDA） and reduced glutathione （GSH） contents, glutathione peroxidase （GSH-Px）, superoxide dismutase （SOD）, myeloperoxidase （MPO） activity and wet/dry （W/D） ratio. RESULTS： All the 30 rats were involved in the result analysis. ①MDA content： The content was significantly higher in the bum group than in the control group and MLT group [（2.02±0.52）, （1.39±0.36）, （1.11±0.29） μmol/g, P 〈 0.01], there was no difference in the contents of control group and MLT group.②GSH content： The content was significantly lower in the bum group than in the control group and MLT group [（7.42±1.01）, （12.67±1.68）, （11.18±1.63） μmol/g, P 〈 0.01], and still lower in MLT group than in the control group（P 〈 0.05）. ③Compared with the control group, GSH-Px and SOD were markedly decreased （P 〈 0.1301） while MPO activity showed a 5.4-fold increase in the bum group （P〈 0.1301）. The GSH-Px activity was higher （P〈 0.01） and MPO level was 21% lower in MLT group than in the bum group （P 〈 0.05）. ④W/D ratio： The ratio was obviously higher in the bum group than in the control group and MLT group （4.42±0.51, 3.57±0.64, 3.98±0.15, P〈 0.01, 0.05） with no significant difference between control group and MLT group. CONCLUSION： MLT may act an effective protection against the acute lung injury by obviously restraining oxidative stress injury and pulmonary oedema in lung tissues of severely-burned rats.