Effects of the gap junction blocker glycyrrhetinic acid on gastrointestinal smooth muscle cells.
Effects of the gap junction blocker glycyrrhetinic acid on gastrointestinal smooth muscle cells.
复制标题
间隙连接阻滞剂甘草次酸对胃肠道平滑肌细胞的影响。
DOI：
10.1152/ajpgi.00389.2004
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Koh,SangDon
中科院分区：
文献类型：
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作者：
Takeda,Yukari;Ward,SeanM;Sanders,KentonM;Koh,SangDon
在胃肠道（GI）的图尼卡肌层中，间隙连接在称为Cajal间质细胞（ICC）的起搏细胞之间以及ICC和平滑肌细胞之间形成低阻力通路。通过这些连接点的耦合促进电慢波传播和平滑肌对肠运动神经的反应。大黄酸（GA）已被证明解偶联间隙连接，但以前的研究表明，在各种组织中的GA明显的非特异性作用。我们测试的影响，GA使用等距力测量，细胞内微电极记录，膜片钳技术，和传播的荧光黄内培养的ICC网络。在小鼠小肠肌肉中，β-GA（10 μM）减少时相收缩和去极化静息膜电位。GA预孵育抑制了荧光黄的扩散，增加了ICC网络的输入电阻，降低了ICC网络的细胞电容，表明GA解偶联了ICC。在离体空肠肌细胞膜片钳实验中，GA以剂量依赖性方式显著降低L型Ca 2+电流，但不影响该电流的电压依赖性。对Ca 2+电流的IC 50为1.9 μM，低于用于阻断间隙连接的浓度。GA也显着增加大电导钙激活的K+电流，但减少净延迟整流K+电流，包括4-氨基吡啶和四乙铵电阻电流。总之，减少阶段性收缩活动的胃肠道肌肉GA可能是其抑制作用的结果间隙连接和电压依赖性钙电流。膜去极化可能是GA对ICC和平滑肌之间的缝隙连接的解偶联作用以及抑制平滑肌细胞中的K+电导的结果。
In the tunica muscularis of the gastrointestinal (GI) tract, gap junctions form low-resistance pathways between pacemaker cells known as interstitial cells of Cajal (ICCs) and between ICC and smooth muscle cells. Coupling via these junctions facilitates electrical slow-wave propagation and responses of smooth muscle to enteric motor nerves. Glycyrrhetinic acid (GA) has been shown to uncouple gap junctions, but previous studies have shown apparent nonspecific effects of GA in a variety of tissues. We tested the effects of GA using isometric force measurements, intracellular microelectrode recordings, the patch-clamp technique, and the spread of Lucifer yellow within cultured ICC networks. In murine small intestinal muscles, β-GA (10 μM) decreased phasic contractions and depolarized resting membrane potential. Preincubation of GA inhibited the spread of Lucifer yellow, increased input resistance, and decreased cell capacitance in ICC networks, suggesting that GA uncoupled ICCs. In patch-clamp experiments of isolated jejunal myocytes, GA significantly decreased L-type Ca2+current in a dose-dependent manner without affecting the voltage dependence of this current. The IC50for Ca2+currents was 1.9 μM, which is lower than the concentrations used to block gap junctions. GA also significantly increased large-conductance Ca2+-activated K+currents but decreased net delayed rectifier K+currents, including 4-aminopyridine and tetraethylammonium-resistant currents. In conclusion, the reduction of phasic contractile activity of GI muscles by GA is likely a consequence of its inhibitory effects on gap junctions and voltage-dependent Ca2+currents. Membrane depolarization may be a consequence of uncoupling effects of GA on gap junctions between ICCs and smooth muscles and inhibition of K+conductances in smooth muscle cells.