Llano I, Marty A, Tanguy J
Pflugers Arch. 1987 Aug;409(4-5):499-506. doi: 10.1007/BF00583807.
Single cells from rat lacrimal glands were studied with the tight-seal whole-cell recording method. Ca-dependent K and Cl currents were measured in response to dialysis with inositoltrisphosphate or GTP gamma S, two compounds known for elevating internal Ca2+ concentration. The activation of the Ca-dependent currents elicited by either compound was partially inhibited by sustained depolarization or by removal of external Ca2+. Conversely, hyperpolarization or removal of external Mg2+ led to augmentations of the Ca-dependent currents. These effects became apparent about 1 min after initiation of cell dialysis with inositoltrisphosphate- or GTP gamma S-containing solutions, and they further developed during the ensuing 10 min. Holding potential and external divalent cations did not affect the Ca-dependent currents elicited by dialysing the cells with strongly buffered solutions containing 0.5 microM free Ca2+. In Ca2+-free external saline, cell currents were independent of the holding potential. It is suggested that InsP3 augments intracellular Ca2+ levels not only by releasing Ca2+ from internal stores but also by slowly increasing the Ca permeability of the plasma membrane. The results indicate that Ca2+ entry through the plasma membrane increases with hyperpolarization. The similarity of the effects seen in InsP3- and GTP gamma S-dialysed cells gives support to the hypothesis that production of the former depends on a GTP-binding protein.
采用全细胞封接记录法对大鼠泪腺的单细胞进行了研究。通过用肌醇三磷酸或鸟苷三磷酸γ - S进行透析来测量钙依赖性钾电流和氯电流，这两种化合物以提高细胞内钙离子浓度而闻名。由这两种化合物引发的钙依赖性电流的激活，会被持续去极化或去除细胞外钙离子部分抑制。相反，超极化或去除细胞外镁离子会导致钙依赖性电流增强。在用含肌醇三磷酸或鸟苷三磷酸γ - S的溶液对细胞进行透析开始约1分钟后，这些效应变得明显，并在随后的10分钟内进一步发展。保持电位和细胞外二价阳离子对在用含0.5微摩尔游离钙离子的强缓冲溶液透析细胞时引发的钙依赖性电流没有影响。在无钙离子的细胞外盐溶液中，细胞电流与保持电位无关。研究表明，肌醇三磷酸不仅通过从细胞内储存库释放钙离子来提高细胞内钙离子水平，还通过缓慢增加质膜的钙离子通透性来实现。结果表明，质膜钙内流随超极化而增加。在经肌醇三磷酸和鸟苷三磷酸γ - S透析的细胞中观察到的效应相似，这支持了前者的产生依赖于一种GTP结合蛋白的假说。
