限制性体位对大鼠膈肌生物力学变化的影响

摘要

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、24h组呼吸频率、潮气量及每分通气量均下降；12h组膈肌条单收缩张力明显降低,低频刺激下张力明显降低,24 h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 effects of restraint position on the changes of diaphragmatic mechanical characteristic in rats, and try to explore the role of nitric oxide (NO). Methods Rat model of restraint position was established. Rats were divided into control group, restraint position 12 h and 24 h groups. The markers of respiratory functions in vivo and the biomechanical markers of diaphragmatic characteristic ex vivo were evaluated. Serum NO levels were measured with spectrophotometry. The expressions of nNOS and iNOS mRNA in diaphragm were detected using RT-PCR. Results Compared with control group, respiratory rate, tidal volume and minute ventilation were significantly decreased in the restraint position 12 h and 24 h groups. Pt of diaphragm significantly decreased and force-generating capacity reduced at low frequency stimulation in 12 h group. Force-generating capacity over the full range reduced at low and high frequency stimulation in 24 h group. Pt of diaphragm in control and restraint position groups increased after L -NNA pre -incubation. Force -frequency relationship after L -NNA pre -incubation reduced in 24 h group. NO level in serum increased significantly in the restraint position groups. Diaphragmatic nNOS mRNA expression was upregulated significantly in the restraint position groups. Conclusion Restraint position induces the decreasement of diaphragmatic contractility and the decreasement is mediated by NO from diaphragm or circulation blood.