Bodily K, Wang Y, Roman R, Sostman A, Fitz J G
Department of Medicine, Duke University Medical Center, Durham, NC, USA.
Hepatology. 1997 Feb;25(2):403-10. doi: 10.1002/hep.510250224.
Liver cell volume and intracellular ion concentrations are maintained within a narrow physiologic range by regulated changes in membrane ion permeability. These studies of homozygous HTC hepatoma cells, a model liver cell line, evaluate the relationship between cell volume and membrane ion permeability, and assess the possibility that cell swelling allows the efflux of the intracellular osmolite taurine through the opening of a conductive pathway. Cell swelling induced by exposure to hypotonic solutions (203 mOsm) caused a rapid increase in cell volume, followed by recovery toward basal values. Volume recovery was inhibited by Cl- depletion or by exposure to the putative Cl- channel blocker 5-nitro-2-(3-phenylpropyl-amino) benzoic acid (NPPB) (25 micromol/L). Swelling increased the efflux rates of 36Cl (181% +/- 15%, P < .01) and 125I (310% +/- 21%, P < .01). In whole cell patch clamp recordings, cell swelling induced by 1) exposure to hypotonic solution or 2) intracellular perfusion with hypertonic sucrose-containing solutions activated an anion-selective current which was outwardly rectified and showed time-dependent inactivation at depolarizing potentials. The current density at -80 mV increased proportionally with increases in the transmembrane osmotic gradient from basal values of -1 pA/pF to maximal values of 70 pA/pF with 100 mmol/L sucrose in the pipette. Basal taurine permeability was low, but cell swelling increased the efflux of [1,2-3H]taurine to 1,587% +/- 172% of basal levels (P < .05). Intracellular perfusion with hypertonic solutions activated currents carried by anionic taurine, with an estimated taurine/Cl- permeability ratio of .88 +/- .17 for whole cell currents. These studies demonstrate that the HTC membrane anion permeability is closely coupled to changes in cell volume, and that the recovery from swelling depends upon activation of anion-selective conductance pathways permeable to both Cl- and taurine.
通过调节膜离子通透性的变化，肝细胞体积和细胞内离子浓度维持在狭窄的生理范围内。对纯合HTC肝癌细胞（一种模型肝细胞系）的这些研究，评估了细胞体积与膜离子通透性之间的关系，并评估了细胞肿胀是否通过开放一条传导途径使细胞内渗透溶质牛磺酸外流的可能性。暴露于低渗溶液（203 mOsm）诱导的细胞肿胀导致细胞体积迅速增加，随后恢复至基础值。Cl- 缺失或暴露于假定的Cl- 通道阻滞剂5-硝基-2-（3-苯丙基氨基）苯甲酸（NPPB）（25 μmol/L）可抑制体积恢复。肿胀增加了36Cl（181%±15%，P <.01）和125I（310%±21%，P <.01）的外流速率。在全细胞膜片钳记录中，1）暴露于低渗溶液或2）用含高渗蔗糖的溶液进行细胞内灌注诱导的细胞肿胀激活了一种阴离子选择性电流，该电流向外整流，并在去极化电位下显示出时间依赖性失活。当移液管中含有100 mmol/L蔗糖时，-80 mV处的电流密度随跨膜渗透梯度从基础值-1 pA/pF增加到最大值70 pA/pF而成比例增加。基础牛磺酸通透性较低，但细胞肿胀使[1,2-3H]牛磺酸的外流增加至基础水平的1587%±172%（P <.05）。用高渗溶液进行细胞内灌注激活了由阴离子牛磺酸携带的电流，全细胞电流的估计牛磺酸/Cl- 通透性比值为0.88±0.17。这些研究表明，HTC膜阴离子通透性与细胞体积变化密切相关，并且肿胀的恢复取决于激活对Cl- 和牛磺酸均通透的阴离子选择性传导途径。
