Saumon G, Martet G, Loiseau P
Institut National de la Santé et de la Recherche Médicale U82, Faculté Xavier Bichat, Paris, France.
Am J Physiol. 1996 Feb;270(2 Pt 1):L183-90. doi: 10.1152/ajplung.1996.270.2.L183.
The glucose concentration in the epithelial lining fluid (ELF) results from a balance between cellular uptake and paracellular leakage. The present study examines whether the ELF glucose concentration can be predicted from the kinetics of glucose transport obtained in fluid-filled lungs. Isolated rat lungs were filled via the trachea with instillate containing 0-10 mM glucose; the perfusate glucose concentration was 10 mM. The rate of glucose removal from airspaces depended on luminal glucose concentration and was saturable [maximum uptake rate = 101 +/- 8.6 mumol.h-1.g dry lung wt-1; apparent Michaelis constant K(m) = 1.5 +/- 0.43 mM; R2 = 0.79]. Glucose removal was inhibited by phloridzin but not by phloretin or by inhibiting glycolysis. The steady-state concentration in fluid-filled lungs was estimated to be 0.15 +/- 0.034 mM. It agreed with that (< 1/20 plasma) calculated using glucose transport kinetics and paracellular permeability. The ELF glucose concentration obtained by bronchoalveolar lavage was 0.39 +/- 0.012 plasma in vivo and 0.39 +/- 0.021 perfusate in air-filled isolated lungs. The equilibrium ELF/perfusate distribution ratio of alpha-methyl-glucose was similar to that of glucose. Thus there is a major difference between the alveolar steady-state glucose concentration in air- and fluid-filled lungs despite similar mechanisms of airspace glucose removal. This suggests that glucose kinetics or access to uptake sites differ in air- and fluid-filled lungs.
上皮衬液（ELF）中的葡萄糖浓度是细胞摄取与细胞旁渗漏之间平衡的结果。本研究探讨是否可以根据在充液肺中获得的葡萄糖转运动力学来预测ELF葡萄糖浓度。通过气管向离体大鼠肺中灌注含0 - 10 mM葡萄糖的灌洗液；灌注液葡萄糖浓度为10 mM。葡萄糖从气腔中清除的速率取决于管腔葡萄糖浓度且具有饱和性[最大摄取速率 = 101 ± 8.6 μmol·h⁻¹·g干肺重⁻¹；表观米氏常数K(m) = 1.5 ± 0.43 mM；R² = 0.79]。葡萄糖的清除受到根皮苷的抑制，但不受根皮素或抑制糖酵解的影响。充液肺中的稳态浓度估计为0.15 ± 0.034 mM。它与使用葡萄糖转运动力学和细胞旁通透性计算得出的值（<血浆的1/20）一致。在体内通过支气管肺泡灌洗获得的ELF葡萄糖浓度为0.39 ± 0.012血浆，在充气离体肺中为0.39 ± 0.021灌注液。α-甲基葡萄糖的平衡ELF/灌注液分布比与葡萄糖相似。因此，尽管气腔葡萄糖清除机制相似，但充气肺和充液肺中的肺泡稳态葡萄糖浓度存在重大差异。这表明气腔葡萄糖动力学或摄取位点的可达性在充气肺和充液肺中有所不同。
