Lyall Vijay, Heck Gerard L, Phan Tam-Hao T, Mummalaneni Shobha, Malik Shahbaz A, Vinnikova Anna K, DeSimone John A
Department of Physiology, Division of Nephrology, Virginia Commonwealth University, Richmond, VA 23298, USA.
J Gen Physiol. 2005 Jun;125(6):569-85. doi: 10.1085/jgp.200409213.
The effect of ethanol on the amiloride- and benzamil (Bz)-insensitive salt taste receptor was investigated by the measurement of intracellular Na(+) activity (Na(+)) in polarized rat fungiform taste receptor cells (TRCs) using fluorescence imaging and by chorda tympani (CT) taste nerve recordings. CT responses were monitored during lingual stimulation with ethanol solutions containing NaCl or KCl. CT responses were recorded in the presence of Bz (a specific blocker of the epithelial Na(+) channel [ENaC]) or the vanilloid receptor-1 (VR-1) antagonists capsazepine or SB-366791, which also block the Bz-insensitive salt taste receptor, a VR-1 variant. CT responses were recorded at 23 degrees C or 42 degrees C (a temperature at which the VR-1 variant salt taste receptor activity is maximally enhanced). In the absence of permeable cations, ethanol induced a transient decrease in TRC volume, and stimulating the tongue with ethanol solutions without added salt elicited only transient phasic CT responses that were insensitive to elevated temperature or SB-366791. Preshrinking TRCs in vivo with hypertonic mannitol (0.5 M) attenuated the magnitude of the phasic CT response, indicating that in the absence of mineral salts, transient phasic CT responses are related to the ethanol-induced osmotic shrinkage of TRCs. In the presence of mineral salts, ethanol increased the Bz-insensitive apical cation flux in TRCs without a change in cell volume, increased transepithelial electrical resistance across the tongue, and elicited CT responses that were similar to salt responses, consisting of both a transient phasic component and a sustained tonic component. Ethanol increased the Bz-insensitive NaCl CT response. This effect was further enhanced by elevating the temperature from 23 degrees C to 42 degrees C, and was blocked by SB-366791. We conclude that in the presence of mineral salts, ethanol modulates the Bz-insensitive VR-1 variant salt taste receptor.
通过使用荧光成像测量极化大鼠菌状味觉受体细胞（TRCs）中的细胞内钠离子活性（[Na⁺]i）以及通过鼓索（CT）味觉神经记录，研究了乙醇对amiloride和苯扎米（Bz）不敏感的盐味受体的影响。在用含有NaCl或KCl的乙醇溶液进行舌部刺激期间监测CT反应。在存在Bz（上皮钠离子通道[ENaC]的特异性阻滞剂）或香草酸受体-1（VR-1）拮抗剂辣椒素或SB-366791的情况下记录CT反应，这些拮抗剂也会阻断Bz不敏感的盐味受体，即VR-1变体。在23℃或42℃（VR-1变体盐味受体活性最大增强的温度）记录CT反应。在不存在可渗透阳离子的情况下，乙醇导致TRC体积短暂减小，用不添加盐的乙醇溶液刺激舌头仅引发对温度升高或SB-366791不敏感的短暂相性CT反应。用高渗甘露醇（0.5M）在体内预收缩TRCs减弱了相性CT反应的幅度，表明在不存在矿物盐的情况下，短暂相性CT反应与乙醇诱导的TRCs渗透收缩有关。在存在矿物盐的情况下，乙醇增加了TRCs中对Bz不敏感的顶端阳离子通量，而细胞体积没有变化，增加了舌部的跨上皮电阻，并引发了类似于盐反应的CT反应，包括短暂相性成分和持续紧张性成分。乙醇增加了对Bz不敏感的NaCl CT反应。将温度从23℃升高到42℃进一步增强了这种效应，并被SB-366791阻断。我们得出结论，在存在矿物盐的情况下，乙醇调节对Bz不敏感的VR-1变体盐味受体。
