不同的通气方式对大鼠肺和肺内毒素受体CD14表达的影响

目的观察不同的通气方式对大鼠肺及对内毒素受体CD14的影响。方法将成年雄性SD大鼠随机分为4组(每组12只):自主呼吸组(R组),不给予机械通气;机械通气组(M组),潮气量(Vt)=12ml/kg,呼气末正压(PEEP)=8mmHg;保护性机械通气组(P组),Vt=6ml/kg,PEEP=0mmHg;大潮气量机械通气组(N组),Vt=40ml/kg,PEEP=0mmHg。每组中6只大鼠实验开始2h后注射50mg/kg伊万斯蓝(EB)。分别于机械通气前(基础值)及机械通气1、2、3h行动脉血气分析,实验3h结束,放血处死大鼠。测定大鼠肺病理形态学积分、肺组织湿/干重比(W/D)、支气管灌洗液(BALF)炎性细胞数、血管壁通透性。酶联免疫分析法(ELISA)测血浆肿瘤坏死因子α(TNF-α)及巨噬细胞炎性蛋白2(MIP-2)浓度。RT-PCR测肺组织内毒素受体CD14的表达,免疫组化法测BALF单核细胞的CD14表达。结果肺病理形态学积分:R组和P组无变化,M组有轻度升高,N组明显高于M组(分别为6·0±1·6、0·7±0·8,t=8,P=0·000)。肺W/D:与R组比较,P组和M组差异无统计学意义;N组高于R组(分别为5·73±0·39、4·91±0·24,t=4·38,P=0·000)。EB:与R组比较,P组和M组差异无统计学意义;N组明显高于R组(分别为84·50±3·01、32·33±1·75,t=36·63,P=0·000)。BALF中WBC:与R组比较,P组无显著变化;M组高于R组(分别为0·83±0·12、0·59±0·62,t=4·272,P=0·02),N组明显高于R组(分别为5·68±0·45、0·59±0·62,t=26·68,P=0·000)。TNF-α在4组都没有测到。MIP-2:P组(35·4±5·3)与R组(31·5±2·4)比较,差异无统计学意义,M组(44·7±6·9)升高(t=4·382,P=0·04),N组(167·7±11·8)明显升高(t=27·779,P=0·000)。BALF中单核细胞的CD14蛋白表达和肺组织CD14基因表达:R组和P组二者表达基本一致,M组蛋白表达与R组差异无统计学意义,但基因表达升高;N组二者表达都显著升高(P=0·000)。结论常规机械通气导致大鼠肺部发生轻度损伤,并可使肺部CD14基因表达上调,但是肺部CD14蛋白表达无改变;大潮气量机械通气导致大鼠的肺部损伤,使肺部CD14表达明显上调。保护性机械通气可使大鼠肺部避免上述改变的发生。

Influence of various ventilation manier on rat's lung and the expression of lung endotoxin receptor CD14 mRNA

OBJECTIVE: To observe the influence of mechanical ventilation (MV) on rat's lung and the expression changes of lung endotoxin receptor CD14 mRNA. METHODS: Forty-eight male SD rats weighing 330-360 g were randomly divided into 4 groups (n = 12 each): group R received no mechanical ventilation, group P received small MV (VT = 6 ml/kg, PEEP = 8 mm Hg), group M received conventional MV (VT = 12 ml/kg, PEEP = 0 mm Hg), and group N received large tidal volume mechanical ventilation (VT = 40 ml/kg, PEEP = 0 mm Hg). The animals were anesthetized with intraperitoneal pentobarbital 100 mg x kg(-1), tracheotomized and mechanically ventilated (I:E = 1:1, FiO2 = 21%). The respiratory rate (RR) of MV was adjusted to maintain the end-tidal carbon dioxide in the rang of 35-45 mm Hg throughout the procedure. Right carotid artery and left femoral vein were cannulated for BP monitoring and fluid and drug administration. 6 rats in each group were injected 50 mg/kg Evans Blue (EB). The experiment was culminated in 3 hours, then the rats were killed by exsanguination via arteria carotis interna. Morphologic change scores of the rats' lungs, wet/dry weight ratio of lung tissue (W/D), bronchial lavage fluid (BALF) inflammatory cell population, and permeability of vessel wall were evaluated. The concentration of TNF-alpha and MIP-2 in the plasma were determined by enzyme immunoassay method (ELISA). The expressions of lung tissue endotoxin receptor CD14 were detected by RT-PCR, macrophage CD14 in BALF was also detected by immunohistochemistry. RESULTS: pulmonary pathomorphology scores: there were no alteration in R group and P group, but it were slightly increased in M group, there was significantly elevated in N group as compare to M group (F = 8.0, P = 0.000). Pulmonary tissue wet/dry weight ratio (W/D): Compare with R group, There was no statistically significant difference in P group and M group; the elevation in N group (t = 4.103, P = 0.02), EB: Compare with R group, There was no statistically significant difference in P group and M group; the obviously elevation in N group (t = 36.634, P = 0.000). WBC in BALF: Compare with R group, there was no change in P group, the elevation in M group (t = 4.272, P = 0.02), there was significantly elevated in N group (F = 26.68, P = 0.000). TNF-alpha had no manifest variation in 4 groups. MIP-2: compare with R group (31.5 +/- 2.4), There was no statistically significant difference in P group (35.4 +/- 5.3), the elevation in M group (44.7 +/- 6.9, t = 7.85, P = 0.04), there was significantly elevated in N group (167.7 +/- 11.8, t = 27.779, P = 0.000). The expressions of macrophage CD14 protein in BALF and lung tissue CD14 mRNA were fundamentally coincident in R group and P group; the expressions of CD14 mRNA were elevated, but the expressions of CD14 protein were no change in M group; the expressions of CD14 in N group manifestly elevated (P = 0.000). CONCLUSIONS: Conventional MV induces minor injury in rat's lung and can up regulate the expression of CD14 mRNA in the lung, but not up regulate the expression of CD14 protein; large tidal volume MV induces injury of rat's lung and evidently up regulates CD14 expression in the lung. Protective MV can avoid the above mentioned variations in rat's lung.