Bai C, Brown L A, Jones D P
Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
Am J Physiol. 1994 Oct;267(4 Pt 1):L447-55. doi: 10.1152/ajplung.1994.267.4.L447.
Glutathione (GSH) is an antioxidant that protects the lung against oxidative-injury. Most cells rely on synthesis of GSH to maintain intracellular supply and only a few cell types take up intact GSH. Although isolated type II cells from rat have a Na(+)-dependent uptake system that transports GSH into the cells against a concentration gradient, it is not known whether this occurs from the vasculature in the intact lung or whether other cell types in the lung also transport GSH. Based on the knowledge that gamma-glutamyl analogues of GSH are also transported by the Na(+)-GSH transporter, a method was developed and used to study the cell specificity of GSH uptake in perfused lung. A stable, fluorescent GSH S-conjugate (GSH-I14) was synthesized and separated from the original dye as analyzed by high-performance liquid chromatography. Studies with isolated alveolar type II cells showed that uptake of GSH-I14 was Na+ dependent and inhibited by GSH. In addition, uptake of GSH by the type II cells was inhibited by GSH-I14. After perfusion of the isolated rat lung with GSH-I14, the conjugate accumulated primarily in the alveolar type II cell as observed by fluorescence microscopy. This was confirmed by isolation of type II cells and measurement of GSH-I14 content. Thus these results show that specificity of GSH transport can be studied with the fluorescent derivative, GSH-I14, and that in the isolated perfused lung type II cells can transport and concentrate GSH-I14 from the perfusate. Quantitative fluorescence microscopy will be required to further determine relative transport activities by other cell types.
谷胱甘肽（GSH）是一种抗氧化剂，可保护肺部免受氧化损伤。大多数细胞依靠GSH的合成来维持细胞内供应，只有少数细胞类型会摄取完整的GSH。尽管从大鼠分离出的II型细胞具有一个依赖Na⁺的摄取系统，该系统能逆浓度梯度将GSH转运到细胞内，但尚不清楚在完整肺中这是否发生于脉管系统，也不清楚肺中的其他细胞类型是否也转运GSH。基于GSH的γ-谷氨酰类似物也由Na⁺-GSH转运体转运这一知识，开发了一种方法并用于研究灌注肺中GSH摄取的细胞特异性。合成了一种稳定的荧光GSH S-缀合物（GSH-I14），并通过高效液相色谱分析将其与原始染料分离。对分离出的肺泡II型细胞的研究表明，GSH-I14的摄取依赖于Na⁺，并受到GSH的抑制。此外，II型细胞对GSH的摄取也受到GSH-I14的抑制。用GSH-I14灌注分离的大鼠肺后，通过荧光显微镜观察到该缀合物主要积聚在肺泡II型细胞中。通过分离II型细胞并测量GSH-I14含量证实了这一点。因此，这些结果表明，可以用荧光衍生物GSH-I14研究GSH转运的特异性，并且在分离的灌注肺中，II型细胞可以从灌流液中转运并浓缩GSH-I14。需要定量荧光显微镜来进一步确定其他细胞类型的相对转运活性。
