Effects of increased intracellular Cl- concentration on membrane responses to acetylcholine in the isolated endothelium of guinea pig mesenteric arteries.
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 IK(Ca) and SK(Ca) channels. The Cl(-) current was partially blocked by tamoxifen, niflumic acid, or DIDS and appears to be produced by Ca(2+)-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.
Yamamoto
Yoshimichi
Y
Laboratory of Physiology, Nagoya City University School of Nursing, Mizuho-ku, Nagoya, 467-8601, Japan. yyamamot@med.nagoya-cu.ac.jp
Suzuki
Hikaru
H
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D018999:Charybdotoxin / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D015640:Ion Channel Gating; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism*; D009544:Niflumic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors; D014665:Vasodilator Agents / Q000494:pharmacology*
D002614:Chelating Agents; D018118:Chloride Channels; D002712:Chlorides; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D014665:Vasodilator Agents; D013629:Tamoxifen; D018999:Charybdotoxin; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D001030:Apamin; D009544:Niflumic Acid; D004533:Egtazic Acid; D000109:Acetylcholine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D002118:Calcium