Physiological Transport Studies Laboratory, Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
Environ Toxicol Pharmacol. 1998 Nov 1;6(3):177-85. doi: 10.1016/s1382-6689(98)00032-5.
Upon inhalation, nitrogen dioxide (NO(2)), a strong oxidizing agent, first comes into contact and reacts with the fluids lining the airways of the respiratory tract. These respiratory tract lining fluids (RTLF) form a barrier between the inhaled toxic pollutant and the epithelium which protects the underlying tissue from inflammation. Proteins, mainly albumin, and antioxidants are the major components of the RTLF. Many studies have utilized human blood plasma to study the interaction of an extracellular fluid with ozone. In this study, we used bronchoalveolar lavage fluids (BALF) as a more specific surrogate for rat RTLF, and we utilized the native fluorescence as a marker to investigate the depletion kinetics of naturally-occurring protein following exposure to NO(2) in a controlled flow reactor system. We also studied the depletion kinetics of albumin in a buffered salt solution. The results indicated that: (1) the decay in fluorescence was linearly dependent on the concentration of NO(2), indicating that protein oxidation was first order with respect to NO(2) concentration in both BALF and in buffered albumin solution; (2) the depletion kinetics of protein in BALF was non-linear with respect to substrate concentration; (3) the rate of protein depletion was much slower in BALF than in a buffered solution of albumin, suggesting that the presence of antioxidants in BALF protected proteins from being oxidized by NO(2); and (4) whereas the addition of ascorbic acid to buffered albumin solution significantly attenuated albumin depletion, the addition of glutathione had no effect. This suggested that the reaction rate constant of ascorbic acid was considerably higher than that of glutathione.
吸入二氧化氮（NO2）后，作为一种强氧化剂，它首先与呼吸道内的气道衬液接触并发生反应。这些呼吸道衬液（RTLF）在吸入的有毒污染物和保护下面组织免受炎症的上皮细胞之间形成一道屏障。蛋白质，主要是白蛋白和抗氧化剂，是 RTLF 的主要成分。许多研究利用人血浆来研究细胞外液与臭氧的相互作用。在这项研究中，我们使用支气管肺泡灌洗液（BALF）作为更具体的大鼠 RTLF 替代物，并利用天然荧光作为标记物，在受控的流动反应器系统中研究了在 NO2 暴露后天然存在的蛋白质的消耗动力学。我们还研究了缓冲盐溶液中白蛋白的消耗动力学。结果表明：（1）荧光的衰减与 NO2 的浓度呈线性关系，表明在 BALF 和缓冲白蛋白溶液中，蛋白质氧化与 NO2 的浓度呈一级关系；（2）BALF 中蛋白质的消耗动力学与底物浓度呈非线性关系；（3）BALF 中蛋白质的消耗速率比缓冲白蛋白溶液中的消耗速率慢得多，这表明 BALF 中的抗氧化剂保护蛋白质免受 NO2 的氧化；（4）尽管向缓冲白蛋白溶液中添加抗坏血酸可显著减少白蛋白的消耗，但添加谷胱甘肽则没有效果。这表明抗坏血酸的反应速率常数明显高于谷胱甘肽。
