Regulation of Slick channels by small changes in cell volume.

In the upper panels, Slick channels were co-expressed with AQP1 in Xenopus laevis oocytes and were activated by a step protocol (−100 mV to +80 mV in 20 mV increments of 500 ms) from a holding potential of −80 mV (4 s). Currents were recorded in isotonic (A), hypotonic (B) or hypertonic (C) media. (D) shows the corresponding I/V relationships under isotonic (black), hypotonic (blue) and hypertonic (red) conditions. Control experiments for native, un-injected oocytes (UI, green) and oocytes only expressing AQP1 (violet) are also shown. In (E) maximal currents were measured at the end of the depolarization to +80 mV under isotonic, hypotonic and hypertonic buffers and the currents were normalized to the current measured at isotonic conditions. Data points in panels (D) and (E) show the mean of 10 independent experiments ± S.E.M. (F) displays a current trace over time for a representative oocyte expressing Slick and AQP1. The expressed Slick channels were activated by depolarization to +80 mV (500 ms) from a holding potential of −80 mV (3 s). The Figure shows the current measured at the end of the depolarization period as a function of time. Changes from isotonic medium to hypo- or hypertonic media are marked with arrows in the figure (the apparent delay from change in medium (arrows) to changes in the recorded currents reflect the “dead volume” in the flow system).在上方面板中，Slick通道与水通道蛋白1（AQP1）在非洲爪蟾（Xenopus laevis）卵母细胞中共表达，并通过阶跃刺激方案从钳制电位−80 mV（维持4 s）激活：以20 mV为增量，从−100 mV阶跃至+80 mV，每个阶跃持续500 ms。电流分别在等渗（A）、低渗（B）或高渗（C）培养液中记录。（D）展示了等渗（黑色）、低渗（蓝色）与高渗（红色）条件下对应的电流-电压（I/V）关系。同时还设置了对照实验：未注射卵母细胞（UI，绿色）以及仅表达AQP1的卵母细胞（紫色）。在（E）中，研究人员在等渗、低渗与高渗缓冲液中，于去极化至+80 mV的末期测量了最大电流，并将其归一至等渗条件下测得的电流值。（D）与（E）中的数据点为10次独立实验的均值±标准误（S.E.M.）。（F）展示了一枚表达Slick通道与AQP1的代表性卵母细胞的随时间变化的电流轨迹：实验中从钳制电位−80 mV（维持3 s）出发，通过去极化至+80 mV（持续500 ms）激活表达的Slick通道，本图展示了去极化末期测得的电流随时间的变化情况。培养液从等渗切换至低渗或高渗的操作在图中以箭头标注，培养液更换至电流变化之间的表观延迟，反映了灌流系统中的死腔体积。