Lung Metabolism: Multiple Indicator Dilution

描述（由申请人提供）：对于继发于慢性阻塞性肺疾病、肺炎或成人呼吸窘迫综合征的肺衰竭患者，低氧血症的常见初始治疗是升高02治疗（高氧）。然而，长时间暴露于高氧环境会导致肺损伤。高氧肺损伤大鼠模型模拟了临床观察到的肺氧毒性的几个方面，其独特之处在于暴露于85% O2 7天可以耐受100% O2的致死效应。相反，暴露于60%氧气环境7天的大鼠对100%氧气环境更敏感。我们的长期目标是阐明对100% O2的耐受性和敏感性的机制。研究表明，高氧诱导氧化还原酶活性的变化，主要发生在肺组织匀浆中，并表明氧化还原酶在大鼠对100% O2的耐受/敏感性中起作用。然而，这些体外研究的结果并不一定能预测高氧诱导的氧化还原酶活性在完整功能肺中的变化。我们提出，在暴露于60% O2和85% O2的大鼠的完整肺中测量氧化还原酶的活性，可以为这些酶在赋予100% O2耐受性或易感性中的作用提供关键见解。因此，具体目标是：1)制定一个实验方案和数学模型，定量评估完整肺中氧化还原酶的活性。2)使用在特定目标1下开发的工具来确定大鼠暴露于60% O2和85% O2 7天对完整肺部氧化还原酶活性的影响。一般的方法是在将靶向氧化还原酶探针注射到暴露于室内空气，60% O2或85% O2的大鼠离体灌注肺的动脉入口时，测量这些探针的静脉流出血浓度。数学模型将用于解释结果数据，并确定完整肺中目标氧化还原酶的活性。统计分析将确定哪些氧化还原酶在暴露于60% O2和85% O2 7天后发生差异。完整肺中氧化还原酶的活性在暴露于60% O2和85% O2时有不同的改变，这表明氧化还原酶在100% O2的易感性或耐受性中起作用。这些结果将为未来的机制研究提供目标，旨在评估差异改变的氧化还原酶作为保护O2毒性的潜在治疗靶点的效用。

DESCRIPTION (provided by applicant): A common initial treatment for hypoxemia in patients with lung failure secondary to chronic obstructive pulmonary diseases, pneumonia, or adult respiratory distress syndrome is elevated 02 therapy (hyperoxia). However, prolonged exposure to hyperoxia causes lung injury. The rat model of hyperoxic lung injury mimics several aspects of lung O2 toxicity observed clinically and is unique in that exposure to 85% O2 for 7 days confers tolerance to the otherwise lethal effects of 100% O2. Conversely, rats exposed to 60% O2 for 7 days become more susceptible to 100% O2. Our long-term goal is to elucidate the mechanisms of tolerance and susceptibility to 100% O2. Studies have demonstrated hyperoxia-induced changes in the activities of redox enzymes, predominantly in lung tissue homogenates, and have suggested that redox enzymes play a role in rat tolerance/susceptibility to 100% O2. However, the results of these in vitro studies do not necessarily predict hyperoxia-induced changes in the activities of redox enzymes in an intact functioning lung. We propose that measurements of the activities of redox enzymes in intact lungs of rats exposed to 60% O2 and 85% O2 can provide critical insights into the role of these enzymes in conferring tolerance or susceptibility to 100% O2. Thus, the specific aims are: 1) Develop an experimental protocol and a mathematical model for quantitative evaluation of the activities of redox enzymes in intact lungs. 2) Use the tools developed under specific aim 1 to determine the effects of 7-day rat exposure to 60% O2 and 85% O2 on the activities of redox enzymes in intact lungs. The general approach will be to measure the venous outflow blood concentrations of probes for targeted redox enzymes during the injection of these probes into the arterial inlet of isolated perfused lungs of rats exposed to room air, 60% O2 or 85% O2. Mathematical modeling will be used to interpret the resulting data and to determine the activities of the targeted redox enzymes in intact lungs. Statistical analysis will determine which redox enzymes are differentially altered by a 7-day exposure to 60% O2 and 85% O2. Demonstration that the activity of a redox enzyme in intact lungs is differentially altered by exposure to 60% O2 and 85% 02 would be suggestive of a role in conferring susceptibility or tolerance to 100% O2. Such results will provide targets for future mechanistic studies designed to evaluate the utility of the differentially altered redox enzymes as potential therapeutic targets for protection from O2 toxicity.