title: The role of K⁺ conductances in regulating membrane excitability in human gastric corpus smooth muscle.
abstract: Changes in resting membrane potential (RMP) regulate membrane excitability. K(+) conductance(s) are one of the main factors in regulating RMP. The functional role of K(+) conductances has not been studied the in human gastric corpus smooth muscles (HGCS). To examine the role of K(+) channels in regulation of RMP in HGCS we employed microelectrode recordings, patch-clamp, and molecular approaches. Tetraethylammonium and charybdotoxin did not affect the RMP, suggesting that BK channels are not involved in regulating RMP. Apamin, a selective small conductance Ca(2+)-activated K(+) channel (SK) blocker, did not show a significant effect on the membrane excitability. 4-Aminopyridine, a Kv channel blocker, caused depolarization and increased the duration of slow wave potentials. 4-Aminopyridine also inhibited a delayed rectifying K(+) current in isolated smooth muscle cells. End-product RT-PCR gel detected Kv1.2 and Kv1.5 in human gastric corpus muscles. Glibenclamide, an ATP-sensitive K(+) channel (KATP) blocker, did not induce depolarization, but nicorandil, a KATP opener, hyperpolarized HGCS, suggesting that KATP are expressed but not basally activated. Kir6.2 transcript, a pore-forming subunit of KATP was expressed in HGCS. A low concentration of Ba(2+), a Kir blocker, induced strong depolarization. Interestingly, Ba(2+)-sensitive currents were minimally expressed in isolated smooth muscle cells under whole-cell patch configuration. KCNJ2 (Kir2.1) transcript was expressed in HGCS. Unique K(+) conductances regulate the RMP in HGCS. Delayed and inwardly rectifying K(+) channels are the main candidates in regulating membrane excitability in HGCS. With the development of cell dispersion techniques of interstitial cells, the cell-specific functional significance will require further analysis.
authors.affiliation: Samsung Biomedical Research Institute and.
authors.forename: Ji Yeon
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Samsung Biomedical Research Institute and.
authors.forename: Eun-Ju
authors.initials: EJ
authors.lastname: Ko
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ki Duck
authors.initials: KD
authors.lastname: Ahn
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Sung
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Medicine, pl.rhee@samsung.com.
authors.forename: Poong-Lyul
authors.initials: PL
authors.lastname: Rhee
mesh_terms: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000378:metabolism; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism*; D005769:Gastrointestinal Motility / Q000187:drug effects; D006801:Humans; D054086:KATP Channels / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D008839:Microelectrodes; D008875:Middle Aged; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D013270:Stomach / Q000187:drug effects; D013997:Time Factors
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D054086:KATP Channels; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D011188:Potassium
keywords: gastrointestinal motility; human stomach; resting membrane potentials; slow wave potentials; smooth muscle cell