INHIBITION OF AN OUTWARDLY RECTIFYING ANION CHANNEL BY HEPES AND RELATED BUFFERS
INHIBITION OF AN OUTWARDLY RECTIFYING ANION CHANNEL BY HEPES AND RELATED BUFFERS
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DOI：
10.1007/bf01871673
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发表时间：
1990-06-01
影响因子：
2.4
通讯作者：
TABCHARANI, JA
中科院分区：
文献类型：
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作者：
HANRAHAN, JW;TABCHARANI, JA
利用膜片钳技术研究了pH缓冲液及相关化合物对外整流阴离子通道电导的影响。在用微量碳酸氢盐缓冲的溶液和含有n -取代牛磺酸（HEPES、MES、BES、TES）和甘氨酸（甘氨酸、比辛和三辛）、Tris和bis-Tris的溶液中测定单通道电流-电压关系。当存在于膜两侧时，HEPES （pKa = 7.55）降低了通道的电导。在细胞质侧（HEPESi）观察到0.6 mM HEPES的显著抑制作用，并且这种作用随着[HEPESi]而增加，因此在逆转电位处的电导减少。25%的10毫米HEPESi和。apprx。70%在非常高的[hespesi]。施加正电压可缓解HEPESi阻滞，但正电流不符合woodhall型阻滞方案，因为计算的解离常数和电距离取决于HEPES浓度。在恒定的[HEPES-]下改变HEPESi总浓度，反之亦然，结果表明阴离子和两性离子（质子化）形式的HEPES都有抑制作用。与相关化合物的结构活性研究表明，从细胞质侧抑制需要磺酸基和杂环脂肪基。TES （pKa = 7.54）、取代甘氨酸缓冲液（pKa = 8.1-8.4）和bis-Tris （pKa = 6.46）对电导没有可测量的影响，似乎适合与该通道一起使用。
The effect of pH buffers and related compounds on the conductance of an outwardly rectifying anion channel has been studied using the patch-clamp technique. Single-channel current-voltage relationship were determined in solutions buffered by trace amounts of bicarbonate and in solutions containing N-substituted taurines (HEPES, MES, BES, TES) and glycines (glycylglycine, bicine and tricine), Tris and bis-Tris at millimolar concentrations. HEPES (pKa = 7.55) reduced the conductance of the channel when present on either side of the membrane. Significant inhibition was observed with 0.6 mM HEPES on the cytoplasmic side (HEPESi) and this effect increased with [HEPESi] so that conductance at the reversal potential was diminished .apprx.25% with 10 mM HEPESi and .apprx.70% at very high [HEPESi]. HEPESi block was relieved by applying positive voltage but positive currents were not consistent with a Woodhull-type blocking scheme in that calculated dissociation constants and electrical distances depended on HEPES concentration. Results obtained by varying total HEPESi concentrations at constant [HEPES-] and vice versa suggest both the anionic and zwitterionic (protonated) forms of HEPES inhibit. Structure-activity studies with related compounds indicate the sulfonate group and heterocyclic aliphatic groups are both required for inhibition from the cytoplasmic side. TES (pKa = 7.54) , substituted glycine buffers (pKa = 8.1-8.4) ad bis-Tris (pKa = 6.46) had no measurable effect on conductance and appear suitable for use with this channel.