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目的观察限制性体位对大鼠膈肌生物力学变化的影响,初步探讨一氧化氮(nitric oxide,NO)的作用。方法复制限制性体位大鼠模型,实验分对照组、限制性体位12h组和限制性体位24h组。检测在体呼吸功能相关指标、离体膈肌条生物力学指标;分光光度法测定血清NO含量;RT-PCR法检测膈肌nNOS和iNOS mRNA表达。结果与对照组比较,限制性体位12、24 h组呼吸频率、潮气量及每分通气量均下降;12 h组膈肌条单收缩张力明显降低,低频刺激下张力明显降低,24h组低频、高频刺激下张力均明显降低;L-NNA预孵育后,膈肌条单收缩张力均增大,24h组张力-频率关系曲线明显下降;限制性体位12、24h组血清NO含量明显升高,膈肌nNOS mRNA表达明显上调。结论膈肌源性NO抑或循环血液来源的NO参与介导限制性体位引起的膈肌收缩功能降低。
Objective To observe the effect of restrictive position on the biomechanical changes of diaphragm in rats and to explore the effect of nitric oxide (NO). METHODS: The rats were divided into control group, restrictive position 12h group and restrictive position 24h group. The indexes of respiratory function in vivo and the biomechanical indexes of isolated diaphragmatic strips were detected. The content of serum NO was measured by spectrophotometry. The expressions of nNOS and iNOS mRNA in diaphragmatic muscle were detected by RT-PCR. Results Compared with the control group, the respiration rate, tidal volume and ventilator per minute were all decreased in the 12 and 24 h groups. The systolic and diastolic tensions of the diaphragmatic muscle strips in 12 h and 24 h groups were significantly lower than those in the control group After pre-incubation with L-NNA, the single contractive tension of diaphragmatic muscle strips increased, while the tension-frequency curve of 24h group decreased obviously. The serum NO levels of 12 and 24 h groups were significantly increased, and the levels of nNOS mRNA expression was significantly increased. CONCLUSION Diaphragmatic-derived nitric oxide (NO) or circulating blood-derived NO is involved in the reduction of diaphragmatic contractile function induced by restrictive posture.