Hypoosmotic stimuli activate a chloride conductance in rat taste cells
Hypoosmotic stimuli activate a chloride conductance in rat taste cells
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DOI：
10.1093/chemse/27.4.383
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发表时间：
2002-05-01
期刊：
影响因子：
3.5
通讯作者：
Gilbertson, TA
中科院分区：
文献类型：
--
作者：
Gilbertson, TA
口腔会处于多种渗透压条件下，但溶液渗透压如何影响味觉系统的性能却鲜为人知。为了阐明低渗刺激影响外周味觉系统的机制，我尝试使用全细胞膜片钳记录技术来描述低渗刺激对单个大鼠味觉受体细胞（TRCs）的影响。在对照生理盐水以及仅渗透压不同（-30、-60和 -90 mOsm）的溶液中，记录对电压斜坡（-90到 +60 mV）产生的电流。在大约三分之二的细胞中，低渗溶液（230 mOsm）使细胞电容增加15%，并激活一种可逆的电导，在刺激持续存在的情况下表现出明显的适应性。在叶状乳头、轮廓乳头、软腭、鼻咽和会厌的味蕾中的味觉细胞中也能引发类似的反应。离子置换实验与以下解释一致：在正常条件下，通过这些明显的体积或牵张激活通道的主要离子是Cl⁻。低渗诱导电流的反转电位与戈德曼 - 霍奇金 - 卡茨恒定电场方程对Cl⁻电导的预测值非常吻合。味觉受体细胞中低渗激活电流的相对通透性顺序为：硫氰酸根⁻≥I⁻>Br⁻>Cl⁻≥F⁻≥羟乙基磺酸根⁻>葡萄糖酸根⁻。药理学实验表明，这种Cl⁻电导被4,4'-二异硫氰酸基 - 2,2'-二磺酸基苯和5 - 硝基 - 3 -（3 - 苯丙基氨基）苯甲酸抑制（EC₅₀分别为1.3和4.6 μM），但不受CdCl₂（300 μM）和GdCl₃（200 μM）的抑制。我假设这种低渗激活的Cl⁻电导与已被充分研究的肿胀激活的Cl⁻电流相似，可能有助于体积调节，并可能代表一种转导机制，通过这种机制，包括水在内的低渗刺激的存在可以在味觉受体细胞中被传递信号。
The oral cavity is subjected to a wide range of osmotic conditions, yet little is known about how solution osmolarity affects performance of the gustatory system. In order to elucidate the mechanism by which hypoosmotic stimuli affect the peripheral taste system, I have attempted to characterize the effects of hypoosmotic stimuli on individual rat taste receptor cells (TRCs) using whole-cell patch clamp recording. Currents elicited in response to voltage ramps (-90 to +60 mV) were recorded in control saline and in solutions varying only in osmolarity (-30, -60 and -90 mOsm). In roughly two-thirds of cells, hypoosmotic solutions (230 mOsm) caused a 15% increase in cell capacitance and activated a reversible conductance that exhibited marked adaptation in the continued presence of the stimulus. Similar responses could be elicited in taste cells from taste buds in the foliate and vallate papillae, the soft palate, the nasopharynx and the epiglottis. Ion substitution experiments were consistent with the interpretation that the predominant ion carried through these apparent volume- or stretch-activated channels was Cl- under normal conditions. Reversal potentials for the hypoosmotic-induced current closely matched those predicted by the Goldman-Hodgkin-Katz constant field equation for a Cl- conductance. The relative permeability sequence of the hypoosmotic-activated current in TRCs was thiocyanate(-) greater than or equal to I- > Br- > Cl- greater than or equal to F- greater than or equal to isethionate(-) > gluconate(-). Pharmacological experiments revealed that this Cl- conductance was inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid and 5-nitro-3-(3-phenylpropylamino)benzoic acid (EC50 = 1.3 and 4.6 muM, respectively), but not by CdCl2 (300 muM) nor GdCl3 (200 muM). I hypothesize that this hypoosmotic-activated Cl- conductance, which is similar to the well-characterized swelling-activated Cl- current, may contribute to volume regulation and could represent the transduction mechanism by which the presence of hypoosmotic stimuli, including water, may be signaled in taste receptor cells.