Saumon G, Basset G, Bouchonnet F, Crone C
Inserm U82 and Département de Physiologie, Faculté Xavier-Bichat, Paris, France.
Pflugers Arch. 1987 Nov;410(4-5):464-70. doi: 10.1007/BF00586526.
The absorption of fluid (bicarbonate-buffered Ringer with 10 mmol/l glucose) instilled into rat lungs is a Na+-coupled process that takes place through two apical transport systems: an amiloride-sensitive Na+ transport and a Na+-glucose co-transport. Fluid absorption in isolated, perfused rat lungs and the permeability to 3H-mannitol of alveolar epithelium were studied in control conditions and during stimulation of the alveolar epithelium by cAMP or isoproterenol. cAMP led to a threefold increase in the rate of fluid absorption and to an increase in the paracellular permeability. A similar response was found following beta-adrenergic stimulation obtained with isoproterenol in the perfusate. The increase in fluid transport was due to enhancement of the amiloride-sensitive component of Na+ transport. The Na+-glucose co-transport which accounts for about 60% of fluid absorption in control conditions was depressed, possibly as a consequence of a depolarization of the apical alveolar cell membrane. Fluid absorption was reduced by 40% by apical amiloride (10(-4) mol/l) in control lungs and to an even larger extent in isoproterenol-stimulated lungs; it was completely abolished by amiloride in cAMP stimulated lungs. Since the Na+-glucose co-transport was still operative, this suggests that a secretory process was triggered. This was confirmed in experiments in which both kinds of transport were inhibited with a combination of amiloride and glucose-free Ringer. In these conditions fluid balance was zero in unstimulated lungs whilst fluid entry into alveoli was observed in isoproterenol and cAMP stimulated lungs.
注入大鼠肺内的液体（含10 mmol/L葡萄糖的碳酸氢盐缓冲林格液）的吸收是一个与Na⁺偶联的过程，通过两种顶端转运系统进行：一种对阿米洛利敏感的Na⁺转运和一种Na⁺-葡萄糖共转运。在对照条件下以及用cAMP或异丙肾上腺素刺激肺泡上皮期间，研究了离体灌注大鼠肺中的液体吸收以及肺泡上皮对³H-甘露醇的通透性。cAMP导致液体吸收速率增加三倍，并使细胞旁通透性增加。在用灌注液中的异丙肾上腺素进行β-肾上腺素能刺激后也发现了类似的反应。液体转运的增加是由于Na⁺转运中对阿米洛利敏感成分的增强。在对照条件下占液体吸收约60%的Na⁺-葡萄糖共转运受到抑制，这可能是顶端肺泡细胞膜去极化的结果。在对照肺中，顶端应用阿米洛利（10⁻⁴ mol/L）使液体吸收减少40%，在异丙肾上腺素刺激的肺中减少程度更大；在cAMP刺激的肺中，阿米洛利使其完全消失。由于Na⁺-葡萄糖共转运仍起作用，这表明触发了一个分泌过程。在用阿米洛利和无糖林格液联合抑制两种转运的实验中证实了这一点。在这些条件下，未刺激的肺中液体平衡为零，而异丙肾上腺素和cAMP刺激的肺中观察到液体进入肺泡。
