Enhancing effects of transition metals on the salt taste responses of single fibers of the frog glossopharyngeal nerve: specificity of and similarities among Ca2+, Mg2+ and Na+ taste responses.
Enhancing effects of transition metals on the salt taste responses of single fibers of the frog glossopharyngeal nerve: specificity of and similarities among Ca2+, Mg2+ and Na+ taste responses.
复制标题
过渡金属对青蛙舌咽神经单纤维盐味反应的增强作用：Ca2+、Mg2+和Na味觉反应的特异性和相似性。
DOI：
10.1093/chemse/19.3.265
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Y. Kitada
中科院分区：
文献类型：
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作者：
Y. Kitada
青蛙舌咽神经对水敏感的纤维(水纤维)也会对CaCl2、MgCl2和氯化钠产生反应。本研究用过渡金属(NiCl2、CoCl2和MnCl2)研究了青蛙味觉细胞膜上阳离子(Ca~(2+)、Mg~(2+)和Na~+)之间的相互作用，这些金属本身在浓度低于5 mM时对产生神经反应几乎没有作用。用吸电极从菌状乳头记录到单个水纤维的单一放电。过渡金属离子(0.05~5.0 mM)对50 mM Ca~(2+)、100 mM Mg~(2+)和500 mM Na~+的反应有明显的增强作用。过渡金属离子的作用总是可逆的。1 mM处过渡金属对50 mM CaCl2、100 mM MgCl2和500 mMNaC l的增强效应排序为NiCl2；CoCl2&gT；MnCl2。对盐分反应有效的过渡金属离子的浓度与钙、镁、钠离子的反应基本一致。结果提示，钙离子、镁离子和钠离子的味觉反应增强是一种共同的机制。Ca~(2+)离子对增强的Na~+反应和增强的Mg~(2+)反应有明显的抑制作用，而Ca~(2+)或Na~+离子对增强的Ca~(2+)反应有抑制作用，提示在Ni~(2+)离子存在时，Ca~(2+)和Mg~(2+)离子之间以及Ca~(2+)和Na~+离子之间存在竞争性拮抗作用。Ni2+离子对低浓度(0.1 mM)CaCl2诱导的Ca~(2+)反应具有双重作用：低浓度(0.02~0.1 mM)时增强，高浓度(0.5~5 mM)时抑制。这些结果表明，过渡金属离子不影响受体-拮抗剂复合体，而只影响受体-激动剂复合体。
Fibers of the frog glossopharyngeal nerve (water fibers) that are sensitive to water also respond to CaCl2, MgCl2 and NaCl. In the present study, interaction among cations (Ca2+, Mg2+ and Na+) on taste cell membrane in frogs was studied using transition metals (NiCl2, CoCl2 and MnCl2), which themselves are barely effective in producing neural response at concentrations below 5 mM. Unitary discharges from single water fibers were recorded from fungiform papillae with suction electrode. Transition metal ions (0.05-5.0 mM) had exclusively enhancing effects on the responses to 50 mM Ca2+, 100 mM Mg2+ and 500 mM Na+. The effects of transition metal ions were always reversible. The rank order of effectiveness of transition metals at 1 mM in the enhancement of the responses to 50 mM CaCl2, 100 mM MgCl2 and 500 mM NaCl was NiCl2 > CoCl2 > MnCl2. The concentration of transition metal ions effective to enhance salt response was almost the same among Ca2+, Mg2+ and Na+ responses. The results suggest that a common mechanism is involved in the enhancement of Ca2+, Mg2+ and Na+ taste responses. The enhanced Mg2+ response and the enhanced Na+ response were greatly inhibited by the addition of Ca2+ ions, and the enhanced Ca2+ response was inhibited by the addition of Mg2+ or Na+ ions, suggesting that competitive antagonism occurs between Ca2+ and Mg2+ ions and between Ca2+ and Na+ ions in the presence of Ni2+ ions. Ni2+ ions had a dual effect on the Ca2+ response induced by low concentration (0.1 mM) of CaCl2: enhancement at lower concentrations (0.02-0.1 mM) of NiCl2 and inhibition at higher concentrations (0.5-5 mM) of NiCl2. The present results suggest that transition metal ions do not affect the receptor-antagonist complex, but affect only the receptor-agonist complex.