Division of Neonatology, University of Leipzig, Leipzig, Germany.
Br J Pharmacol. 2013 Mar;168(6):1329-40. doi: 10.1111/bph.12027.
Pharmacological enhancement of vectorial Na⁺ transport may be useful to increase alveolar fluid clearance. Herein, we investigated the influence of the benzimidazolones 1-ethyl-1,3-dihydro-2-benzimidazolone (1-EBIO), 5,6-dichloro-1-EBIO (DC-EBIO) and chlorzoxazone on vectorial epithelial Na⁺ transport.
Effects on vectorial Na⁺ transport and amiloride-sensitive apical membrane Na⁺ permeability were determined by measuring short-circuit currents (I(SC)) in rat fetal distal lung epithelial (FDLE) monolayers. Furthermore, amiloride-sensitive membrane conductance and the open probability of epithelial Na⁺ channels (ENaC) were determined by patch clamp experiments using A549 cells.
I(SC) was increased by approximately 50% after addition of 1-EBIO, DC-EBIO and chlorzoxazone. With permeabilized basolateral membranes in the presence of a 145:5 apical to basolateral Na⁺ gradient, the benzimidazolones markedly increased amiloride-sensitive I(SC). 5-(N-Ethyl-N-isopropyl)amiloride-induced inhibition of I(SC) was not affected. The benzamil-sensitive I(SC) was increased in benzimidazolone-stimulated monolayers. Pretreating the apical membrane with amiloride, which inhibits ENaC, completely prevented the stimulating effects of benzimidazolones on I(SC). Furthermore, 1-EBIO (1 mM) and DC-EBIO (0.1 mM) significantly increased (threefold) the open probability of ENaC without influencing current amplitude. Whole cell measurements showed that DC-EBIO (0.1 mM) induced an amiloride-sensitive increase in membrane conductance.
Benzimidazolones have a stimulating effect on vectorial Na⁺ transport. The antagonist sensitivity of this effect suggests the benzimidazolones elicit this action by activating the highly selective ENaC currents. Thus, the results demonstrate a possible new strategy for directly enhancing epithelial Na⁺ transport.
增强载体 Na⁺转运的药理学作用可能有助于增加肺泡液体清除率。在此，我们研究了苯并咪唑酮 1-乙基-1,3-二氢-2-苯并咪唑酮（1-EBIO）、5,6-二氯-1-EBIO（DC-EBIO）和氯唑沙宗对载体上皮 Na⁺转运的影响。
通过测量大鼠胎肺上皮（FDLE）单层的短路电流（I（SC））来确定对载体 Na⁺转运和阿米洛利敏感的顶端膜 Na⁺通透性的影响。此外，通过使用 A549 细胞进行膜片钳实验测定阿米洛利敏感的膜电导和上皮 Na⁺通道（ENaC）的开放概率。
添加 1-EBIO、DC-EBIO 和氯唑沙宗后，I（SC）增加了约 50%。在存在 145:5 顶端到基底外侧 Na⁺梯度的通透性基底外侧膜的情况下，苯并咪唑酮明显增加了阿米洛利敏感的 I（SC）。5-（N-乙基-N-异丙基）阿米洛利抑制 I（SC）的抑制作用不受影响。在苯并咪唑酮刺激的单层中，苯并咪嗪敏感的 I（SC）增加。在用阿米洛利预处理顶端膜后，阿米洛利抑制 ENaC，完全阻止了苯并咪唑酮对 I（SC）的刺激作用。此外，1-EBIO（1 mM）和 DC-EBIO（0.1 mM）显著增加（三倍）ENaC 的开放概率，而不影响电流幅度。全细胞测量表明，DC-EBIO（0.1 mM）诱导阿米洛利敏感的膜电导增加。
苯并咪唑酮对载体 Na⁺转运具有刺激作用。这种作用的拮抗剂敏感性表明，苯并咪唑酮通过激活高度选择性的 ENaC 电流来引发这种作用。因此，这些结果表明了一种直接增强上皮 Na⁺转运的新策略。
