Mustafina Alsu N, Yakovlev Aleksey V, Gaifullina Aisylu Sh, Weiger Thomas M, Hermann Anton, Sitdikova Guzel F
Department of Human and Animal Physiology, Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008, Kazan, Kremlevskii Str., 18, Russia.
Department of Cell Biology, University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria.
Biochem Biophys Res Commun. 2015 Oct 2;465(4):825-31. doi: 10.1016/j.bbrc.2015.08.095. Epub 2015 Aug 28.
The aim of the present study was to evaluate the effects of hydrogen sulfide (H2S) on the membrane potential, action potential discharge and exocytosis of secretory granules in neurosecretory pituitary tumor cells (GH3). The H2S donor - sodium hydrosulfide (NaHS) induced membrane hyperpolarization, followed by truncation of spontaneous electrical activity and decrease of the membrane resistance. The NaHS effect was dose-dependent with an EC50 of 152 μM (equals effective H2S of 16-19 μM). NaHS effects were not altered after inhibition of maxi conductance calcium-activated potassium (BK) channels by tetraethylammonium or paxilline, but were significantly reduced after inhibition or activation of ATP-dependent potassium channels (KATP) by glibenclamide or by diazoxide, respectively. In whole-cell recordings NaHS increased the amplitude of KATP currents, induced by hyperpolarizing pulses and subsequent application of glibenclamide decreased currents to control levels. Using the fluorescent dye FM 1-43 exocytosis of secretory granules was analyzed in basal and stimulated conditions (high K(+) external solution). Prior application of NaHS decreased the fluorescence of the cell membrane in both conditions which links with activation of KATP currents (basal secretion) and activation of KATP currents and BK-currents (stimulated exocytosis). We suggest that H2S induces hyperpolarization of GH3 cells by activation of KATP channels which results in a truncation of spontaneous action potentials and a decrease of hormone release.
本研究的目的是评估硫化氢（H₂S）对神经分泌性垂体肿瘤细胞（GH3）的膜电位、动作电位发放及分泌颗粒胞吐作用的影响。H₂S供体——硫氢化钠（NaHS）可诱导膜超极化，随后自发电活动截断，膜电阻降低。NaHS的作用呈剂量依赖性，半数有效浓度（EC50）为152 μM（相当于有效H₂S浓度为16 - 19 μM）。用四乙铵或放线菌酮抑制大电导钙激活钾（BK）通道后，NaHS的作用未改变，但分别用格列本脲或二氮嗪抑制或激活ATP依赖性钾通道（KATP）后，NaHS的作用显著减弱。在全细胞记录中，NaHS增加了超极化脉冲诱导的KATP电流幅度，随后应用格列本脲可使电流降至对照水平。使用荧光染料FM 1 - 43分析了基础条件和刺激条件（高钾细胞外液）下分泌颗粒的胞吐作用。预先应用NaHS在两种条件下均降低了细胞膜荧光，这与KATP电流激活（基础分泌）以及KATP电流和BK电流激活（刺激分泌）有关。我们认为，H₂S通过激活KATP通道诱导GH3细胞超极化，这导致自发动作电位截断及激素释放减少。
