Molecular mechanism of gustatory transduction in taste cells

1.用电生理技术研究了蛙类味觉细胞的各种离子通道和泵及其味觉转导机制。我们在味觉细胞膜上发现了电压门控性钠通道和四种类型的钾通道(钙激活；延迟整流；瞬变；内向整流)。盐对青蛙味觉细胞反应的转导与顶端感受膜的阳离子通道和阴离子通道以及基底侧膜的TTX不敏感的钠通道有关。奎宁-盐酸盐进入蛙类味觉细胞的反应与细胞内氯离子通过顶端感受器膜的释放有关。半乳糖转导到味觉细胞的反应与细胞内OH^-的释放或表面H^+的进入或两者都通过顶端感受器膜有关。HCl传导到味觉细胞的反应与基侧膜上的通道和泵无关，而与顶端感受膜上的钙通道和质子泵有关。前者的贡献远大于后者，用Cd~(2+)和Gt~(2+)阻断Ca~(2+)通道后，酸诱导的受体电位显著降低。用膜片电极同时记录味觉感受器膜电流和味觉刺激，发现氯化钠刺激进入味觉细胞反应与氯化钠门控K~+通道对单价阳离子具有较低的选择性有关。

1. We investigated kinds of ionic channels and pumps and the gustatory transduction mechanisms in frog taste cells with electrophysiological techniques.2. We found voltage-gated Na channel and four types of K channels (Ca-activated ; delayed rectifier ; transient ; inward rectifier) in the taste cell membrane.3. Transduction of NaCl into a frog taste cell response is concerned with cation and anion channels of the apical receptive membrane and TTX insensitive Na channel of the basolateral membrane.4. Transduction of quinine-HCl into a frog taste cell response is concerned with a release of intracellular Cl^- through the apical receptive membrane.5. Transduction of galactose into the taste cell response is concerned with a release of intracellular OH^- or an entry of superficial H^+ or both through the apical receptive membrane.6. Transduction of HCl into the taste cell response is not concerned with channels and pumps at the basolateral membrane, but with Ca channels and proton pumps at the apical receptive membrane. The contribution of the former is much larger than that of the latter, and blocking the Ca channels with Cd^<2+> greatly reduced the acid-induced receptor potential.7. By simultaneous current recording and gustatory stimulation of the taste receptor membrane with a patch pipette, it was found that transduction of NaCl stimuli into the taste cell response is concerned with the NaCl-gated K^+ channels having a relatively low selectivity to monovalent cations.