Kibble J D, Greenwood S L, Clarson L H, Sibley C P
School of Biological Sciences, Cell Physiology Group, University of Manchester, G.38, Stopford Building, Oxford Road, Manchester, M13 9PT, United Kingdom.
J Membr Biol. 1996 May;151(2):131-8. doi: 10.1007/s002329900064.
Whole-cell patch clamp experiments were performed on cultured human cytotrophoblast cells incubated for 24-48 hr after their isolation from term placentas. Cl--selective currents were examined using K+-free solutions. Under nonstimulated conditions, most cells initially expressed only small background leak currents. However, inclusion of 0.2 mM GTPgammaS in the electrode solution caused activation of an outwardly rectifying conductance which showed marked time-dependent activation at depolarized potentials above +20 mV. Stimulation of this conductance by GTPgammaS was found to be Ca2+-dependent since GTPgammaS failed to activate currents when included in a Ca2+-free electrode solution. In addition, similar currents could be activated by increasing the [Ca2+] of the pipette solution to 500 nM. The Ca2+-activated conductance was judged to be Cl--selective, since reversal potentials were predicted by Nernst equilibrium potentials for Cl-. This conductance could also be reversibly inhibited by addition of the anion channel blocker DIDS to the bath solution at a dose of 100 microM. Preliminary experiments indicated the presence of a second whole-cell anion conductance in human cytotrophoblast cells, which may be activated by cell swelling. Possible roles for the Ca2+-activated Cl- conductance in human placental trophoblast are discussed.
全细胞膜片钳实验在从足月胎盘分离后培养24 - 48小时的人细胞滋养层细胞上进行。使用无钾溶液检测氯离子选择性电流。在非刺激条件下，大多数细胞最初仅表现出小的背景漏电流。然而，在电极溶液中加入0.2 mM GTPγS会激活一种外向整流电导，该电导在高于 +20 mV的去极化电位下表现出明显的时间依赖性激活。发现GTPγS对这种电导的刺激是Ca²⁺依赖性的，因为当GTPγS包含在无Ca²⁺的电极溶液中时未能激活电流。此外，通过将移液管溶液的[Ca²⁺]增加到500 nM可以激活类似的电流。由于反转电位由氯离子的能斯特平衡电位预测，因此判断Ca²⁺激活的电导是氯离子选择性的。通过以100 μM的剂量向浴液中加入阴离子通道阻滞剂DIDS，这种电导也可以被可逆地抑制。初步实验表明人细胞滋养层细胞中存在第二种全细胞阴离子电导，其可能由细胞肿胀激活。讨论了Ca²⁺激活的氯离子电导在人胎盘滋养层中的可能作用。
