Cott G R, Sugahara K, Mason R J
Am J Physiol. 1986 Feb;250(2 Pt 1):C222-7. doi: 10.1152/ajpcell.1986.250.2.C222.
The active transcellular transport of electrolytes across the alveolar epithelium probably plays an important role in alveolar fluid homeostasis by helping to maintain the alveolus relatively free of fluid. To better understand the factors regulating active ion transport across alveolar epithelial cells, we examined the effect of a number of pharmacologically active agents on the bioelectric properties of alveolar type II cells in primary culture. Alveolar type II cells were isolated from adult male rats and cultured on collagen-coated Millipore filters for 6-14 days. The bioelectric properties of these monolayers were determined in Ussing-type chambers. The addition of 10(-3) M 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) increased the short-circuit current (Isc) from 2.9 +/- 0.75 to 6.9 +/- 0.73 microA/cm2 (means +/- SE; n = 8) and decreased the transepithelial resistance. Cholera toxin, 3-isobutyl-1-methylxanthine, and terbutaline sulfate produced similar increases in Isc and decreases in resistance. The Isc stimulated by 8-BrcAMP was Na but not Cl dependent and could be blocked by amiloride but not by furosemide. Thus 8-BrcAMP and agents that increase intracellular cAMP can stimulate a Na-dependent net active ion transport across alveolar type II cell monolayers. Similar regulatory mechanisms may be involved in controlling solute and fluid movement across the alveolar epithelium in vivo.
电解质跨肺泡上皮细胞的主动跨细胞转运可能通过帮助维持肺泡相对无液状态，在肺泡液体稳态中发挥重要作用。为了更好地理解调节跨肺泡上皮细胞主动离子转运的因素，我们研究了多种药理活性剂对原代培养的II型肺泡细胞生物电特性的影响。从成年雄性大鼠分离出II型肺泡细胞，并在胶原包被的密理博滤膜上培养6 - 14天。在尤斯灌流室中测定这些单层细胞的生物电特性。加入10(-3)M 8 - 溴腺苷3',5'-环磷酸（8 - BrcAMP）可使短路电流（Isc）从2.9±0.75微安/平方厘米增加到6.9±0.73微安/平方厘米（均值±标准误；n = 8），并降低跨上皮电阻。霍乱毒素、3 - 异丁基 - 1 - 甲基黄嘌呤和硫酸特布他林也使Isc有类似增加且电阻降低。8 - BrcAMP刺激的Isc依赖于Na而非Cl，且可被氨氯吡咪阻断，但不能被呋塞米阻断。因此，8 - BrcAMP和增加细胞内cAMP的试剂可刺激跨II型肺泡细胞单层的Na依赖性净主动离子转运。类似的调节机制可能参与体内控制溶质和液体跨肺泡上皮的移动。
