title: ERG K+ channels modulate the electrical and contractile activities of gallbladder smooth muscle.
abstract: The current study was undertaken to test the existence and possible role of ether-a-go-go-related gene 1 (ERG1) protein K(+) channels in gallbladder smooth muscle (GBSM). Transcripts encoding ERG1 were detected in human, mouse, and guinea pig GBSM, and ERG1 immunoreactivity was observed in GBSM cells. In intracellular voltage recordings, addition of E-4031 (100 nM-1 microM) or cisapride (100 nM-2 microM) caused concentration-dependent excitation of guinea pig GBSM that was not affected by 500 nM TTX + 5 microM atropine, and E-4031 also depolarized the resting membrane potential. In muscle strip studies, E-4031 either induced phasic contractions or significantly increased the amplitude of phasic contractions in spontaneously active tissues (P = 0.001). E-4031 also potentiated bethanechol-induced contractions. In conclusion, ERG1 channels are expressed in the GBSM, where they play a role in excitation-contraction coupling probably by contributing to repolarization of the plateau phase of the action potential and to the resting membrane potential.
authors.affiliation: Department of Anatomy and Neurobiology, The University of Vermont, Burlington, VT 05405, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Parr
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Pozo
authors.forename: Burton
authors.initials: B
authors.lastname: Horowitz
authors.forename: Mark T
authors.initials: MT
authors.lastname: Nelson
authors.forename: Gary M
authors.initials: GM
authors.lastname: Mawe
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D005704:Gallbladder / Q000294:innervation / Q000502:physiology*; D006168:Guinea Pigs; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D018721:Muscarinic Agonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C000606915:Kcnh2 protein, mouse; D018721:Muscarinic Agonists; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D018723:Bethanechol