Olivero Pablo, Leiva-Salcedo Elías, Devoto Luigi, Stutzin Andrés
Centro de Estudios Moleculares de la Célula and Instituto de Ciencias Biomédicas, Escuela de Medicina, Universidad de Valparaíso, Valparaíso, Chile.
Endocrinology. 2008 Sep;149(9):4680-7. doi: 10.1210/en.2008-0303. Epub 2008 May 22.
Chloride permeability pathways and progesterone (P4) secretion elicited by human chorionic gonadotropin (hCG) in human granulosa cells were studied by electrophysiological techniques and single-cell volume, membrane potential and Ca2+i measurements. Reduction in extracellular Cl(-) and equimolar substitution by the membrane-impermeant anions glutamate or gluconate significantly increased hCG-stimulated P4 accumulation. A similar result was achieved by exposing the cells to hCG in the presence of a hypotonic extracellular solution. Conversely, P4 accumulation was drastically reduced in cells challenged with hCG exposed to a hypertonic solution. Furthermore, conventional Cl(-) channel inhibitors abolished hCG-mediated P4 secretion. In contrast, 25-hydroxycholesterol-mediated P4 accumulation was unaffected by Cl(-) channel blockers. In human granulosa cells, hCG triggered the activation of a tamoxifen-sensitive outwardly rectifying Cl(-) current comparable to the volume-sensitive outwardly rectifying Cl(-) current. Exposure of human granulosa cells to hCG induced a rapid 4,4'-diisothiocyanatostilbene-2,2-disulphonic acid-sensitive cell membrane depolarization that was paralleled with an approximately 20% decrease in cell volume. Treatment with hCG evoked oscillatory and nonoscillatory intracellular Ca2+ signals in human granulosa cells. Extracellular Ca2+ removal and 4,4'-diisothiocyanatostilbene-2,2-disulphonic acid abolished the nonoscillatory component while leaving the Ca2+ oscillations unaffected. It is concluded that human granulosa cells express functional the volume-sensitive outwardly rectifying Cl(-) channels that are activated by hCG, which are critical for plasma membrane potential changes, Ca2+ influx, and P4 production.
采用电生理技术以及单细胞体积、膜电位和细胞内钙离子浓度测量方法，研究了人绒毛膜促性腺激素（hCG）诱导人颗粒细胞中氯离子通透性途径和孕酮（P4）分泌情况。细胞外氯离子减少以及用膜不通透性阴离子谷氨酸盐或葡萄糖酸盐进行等摩尔替代，可显著增加hCG刺激的P4积累。在低渗细胞外溶液存在的情况下，将细胞暴露于hCG也可得到类似结果。相反，在高渗溶液中暴露于hCG的细胞中，P4积累大幅减少。此外，传统的氯离子通道抑制剂可消除hCG介导的P4分泌。相比之下，25-羟胆固醇介导的P4积累不受氯离子通道阻滞剂的影响。在人颗粒细胞中，hCG触发了一种对他莫昔芬敏感的外向整流氯离子电流的激活，该电流与容积敏感外向整流氯离子电流相当。将人颗粒细胞暴露于hCG会诱导快速的4,4'-二异硫氰酸根合芪-2,2-二磺酸敏感的细胞膜去极化，同时细胞体积大约减少20%。用hCG处理可诱发人颗粒细胞中振荡性和非振荡性的细胞内钙离子信号。去除细胞外钙离子和4,4'-二异硫氰酸根合芪-2,2-二磺酸可消除非振荡成分，而不影响钙离子振荡。研究得出结论，人颗粒细胞表达功能性的容积敏感外向整流氯离子通道，该通道可被hCG激活，对质膜电位变化、钙离子内流和P4产生至关重要。
