Lung Metabolism: Multiple Indicator Dilution

描述（由申请人提供）：慢性阻塞性肺疾病、肺炎或成人呼吸窘迫综合征继发性肺衰竭患者的低氧血症的常见初始治疗是升高O2治疗（高氧）。然而，长时间暴露于高氧会导致肺损伤。高氧肺损伤的大鼠模型模拟了临床观察到的肺O2毒性的几个方面，其独特之处在于暴露于85%O2 7天可耐受100%O2的其他致死作用。相反，暴露于60% O2 7天的大鼠对100% O2更敏感。我们的长期目标是阐明耐受性和敏感性的机制，以100%O2。研究表明，高氧诱导的氧化还原酶活性的变化，主要是在肺组织匀浆中，并已表明，氧化还原酶在大鼠耐受性/敏感性100%O2的作用。然而，这些体外研究的结果并不一定能预测高氧诱导的完整功能肺中氧化还原酶活性的变化。我们建议，暴露于60%O2和85%O2的大鼠完整的肺中的氧化还原酶的活性的测量可以提供关键的见解，这些酶的作用，赋予耐受性或敏感性100%O2。因此，具体的目标是：1）建立一个实验方案和数学模型，用于定量评价完整肺中氧化还原酶的活性。2)使用在具体目标1下开发的工具，确定大鼠暴露于60% O2和85% O2 7天对完整肺中氧化还原酶活性的影响。一般方法是在将这些探针注射到暴露于室内空气、60% O2或85% O2的大鼠的隔离灌注肺的动脉入口期间，测量靶向氧化还原酶的探针的静脉流出血液浓度。将使用数学建模来解释所得数据并确定完整肺中靶向氧化还原酶的活性。统计分析将确定哪些氧化还原酶在暴露于60% O2和85% O2 7天后发生差异性改变。完整肺中氧化还原酶的活性通过暴露于60%O2和85%O2而不同地改变的证明将暗示赋予对100%O2的敏感性或耐受性的作用。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免受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.