Effects of Increased Intracellular Cl〔-〕 Concentration on Membrane Responses to Acetylcholine in the Isolated Endothelium of Guinea Pig Mesenteric Arteries

  • Yamamoto Yoshimichi
    Laboratory of Physiology, Nagoya City University School of Nursing Department of Regulatory Cell Physiology, Nagoya City University Graduate School of Medical Sciences
  • Suzuki Hikaru
    Department of Regulatory Cell Physiology, Nagoya City University Graduate School of Medical Sciences

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タイトル別名
  • Effects of Increased Intracellular Cl- Concentration on Membrane Responses to Acetylcholine in the Isolated Endothelium of Guinea Pig Mesenteric Arteries
  • Effects of Increased Intracellular Cl− Concentration on Membrane Responses to Acetylcholine in the Isolated Endothelium of Guinea Pig Mesenteric Arteries

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ACh-induced membrane responses in vascular endothelial cells that have been reported vary between preparations from a sustained hyperpolarization to a transient hyperpolarization followed by a depolarization; the reason for this variation is unknown. Using the perforated whole-cell clamp technique, we investigated ACh-induced membrane currents in freshly isolated endothelial layers having a resting membrane potential of less negative than −10 mV. A group of cells was electrically isolated using a wide-bore micropipette, and their membrane potential was well controlled. ACh activated K+ and Cl currents simultaneously. The K+ current was blocked by a combination of charybdotoxin and apamin and appears to result from the opening of IKCa and SKCa channels. The Cl current was partially blocked by tamoxifen, niflumic acid, or DIDS and appears to be produced by Ca2+-activated Cl channels. When the pipettes contained 20 mM Cl, the ACh-induced K+ conductance started decreasing during a 1-min application of ACh while the Cl conductance continued, making the ACh-induced hyperpolarization sustained. When the pipettes contained 150 mM Cl, both conductances started decreasing during a 1-min application of ACh, making the ACh-induced hyperpolarization small and transient. [Cl]i is very likely modified by experimental procedures such as the cell isolation and the intracellular dialysis with the pipette solution. Such a variability in [Cl]i may be one of the reasons for the variations in the ACh-induced membrane response.<br>

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