BACKGROUND Alterations of bioelectrical properties of cells and tissues are known to function as wide-ranging signals during development, regeneration and wound-healing in several species. The Drosophila follicle-cell epithelium provides an appropriate model system for studying the potential role of electrochemical signals, like intracellular pH (pHi) and membrane potential (Vmem), during development. Therefore, we analysed stage-specific gradients of pHi and Vmem as well as their dependence on specific ion-transport mechanisms. RESULTS Using fluorescent indicators, we found distinct alterations of pHi- and Vmem-patterns during stages 8 to 12 of oogenesis. To determine the roles of relevant ion-transport mechanisms in regulating pHi and Vmem and in establishing stage-specific antero-posterior and dorso-ventral gradients, we used inhibitors of Na+/H+-exchangers and Na+-channels (amiloride), V-ATPases (bafilomycin), ATP-sensitive K+-channels (glibenclamide), voltage-dependent L-type Ca2+-channels (verapamil), Cl--channels (9-anthroic acid) and Na+/K+/2Cl--cotransporters (furosemide). Either pHi or Vmem or both parameters were affected by each tested inhibitor. While the inhibition of Na+/H+-exchangers (NHE) and amiloride-sensitive Na+-channels or of V-ATPases resulted in relative acidification, inhibiting the other ion-transport mechanisms led to relative alkalisation. The most prominent effects on pHi were obtained by inhibiting Na+/K+/2Cl--cotransporters or ATP-sensitive K+-channels. Vmem was most efficiently hyperpolarised by inhibiting voltage-dependent L-type Ca2+-channels or ATP-sensitive K+-channels, whereas the impact of the other ion-transport mechanisms was smaller. In case of very prominent effects of inhibitors on pHi and/or Vmem, we also found strong influences on the antero-posterior and dorso-ventral pHi- and/or Vmem-gradients. For example, inhibiting ATP-sensitive K+-channels strongly enhanced both pHi-gradients (increasing alkalisation) and reduced both Vmem-gradients (increasing hyperpolarisation). Similarly, inhibiting Na+/K+/2Cl--cotransporters strongly enhanced both pHi-gradients and reduced the antero-posterior Vmem-gradient. To minor extents, both pHi-gradients were enhanced and both Vmem-gradients were reduced by inhibiting voltage-dependent L-type Ca2+-channels, whereas only both pHi-gradients were reduced (increasing acidification) by inhibiting V-ATPases or NHE and Na+-channels. CONCLUSIONS Our data show that in the Drosophila follicle-cell epithelium stage-specific pHi- and Vmem-gradients develop which result from the activity of several ion-transport mechanisms. These gradients are supposed to represent important bioelectrical cues during oogenesis, e.g., by serving as electrochemical prepatterns in modifying cell polarity and cytoskeletal organisation.

中文翻译：

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果蝇卵子发生过程中的电化学模式：离子转运机制在卵泡细胞上皮细胞中产生阶段性的pH梯度和膜电位。

背景技术已知细胞和组织的生物电特性的改变在几种物种的发育，再生和伤口愈合过程中起着广泛的信号的作用。果蝇的卵泡细胞上皮细胞提供了一个合适的模型系统，用于研究发育过程中电化学信号的潜在作用，例如细胞内pH（pHi）和膜电位（Vmem）。因此，我们分析了pHi和Vmem的阶段特定梯度及其对特定离子传输机制的依赖性。结果使用荧光指示剂，我们发现在卵子发生的第8到第12阶段，pHi和Vmem模式发生了明显的变化。要确定相关的离子转运机制在调节pHi和Vmem以及建立阶段特异性前后-后-背-腹梯度中的作用，我们使用了Na + / H +交换子和Na +通道（阿米洛利），V-ATPases（巴非霉素），ATP敏感的K +通道（格列本脲），电压依赖性L型Ca2 +通道（维拉帕米），Cl--的抑制剂通道（9-蒽甲酸）和Na + / K + / 2Cl-共转运蛋白（速尿）。pHi或Vmem或两个参数均受每种测试抑制剂的影响。虽然对Na + / H +交换子（NHE）和阿米洛利敏感的Na +通道或V-ATPase的抑制导致相对酸化，但抑制其他离子迁移机制却导致相对碱化。对pHi的最显着影响是通过抑制Na + / K + / 2Cl-共转运蛋白或ATP敏感的K +通道获得的。Vmem通过抑制电压依赖性L型Ca2 +通道或ATP敏感的K +通道而最有效地超极化，而其他离子传输机制的影响较小。如果抑制剂对pHi和/或Vmem有非常显着的作用，我们还发现了对前后，后腹和pHi和/或Vmem梯度的强烈影响。例如，抑制ATP敏感的K +通道会极大地增强两个pHi梯度（增加碱化）并降低两个Vmem梯度（增加超极化）。类似地，抑制Na + / K + / 2Cl-共转运蛋白可显着增强pHi梯度和降低前后Vmem梯度。在较小程度上，通过抑制电压依赖性L型Ca2 +通道，两个pHi梯度都增加了，并且两个Vmem梯度都降低了，而通过抑制V-ATPases或NHE和Na +，只有两个pHi梯度都降低了（增加了酸化作用）。 -频道。结论我们的数据表明，在果蝇的卵泡细胞上皮阶段，出现了特定的pHi和Vmem梯度，这是由于几种离子转运机制的活性所致。这些梯度被认为代表了卵子发生过程中的重要生物电信号，例如，通过充当修饰细胞极性和细胞骨架组织的电化学前兆。