title: Quinidine-sensitive K+ channels in the basolateral membrane of embryonic coprodeum epithelium: regulation by aldosterone and thyroxine.
abstract: Basolateral K+ channels and their regulation during aldosterone- and thyroxine-stimulated Na+ transport were studied in the lower intestinal epithelium (coprodeum) of embryonic chicken in vitro. Isolated tissues of the coprodeum were mounted in Ussing chambers and investigated under voltage-clamped conditions. Simultaneous stimulation with aldosterone (1 mumol.l-1) and thyroxine (1 mumol.l-1) raised short-circuit current after a 1- to 2-h latent period. Maximal values were reached after 6-7 h of hormonal treatment, at which time transepithelial Na+ absorption was more than tripled (77 +/- 11 microA.cm-2) compared to control (24 +/- 8 microA.cm-2). K+ currents across the basolateral membrane were investigated after permeabilizing the apical membrane with the pore-forming antibiotic amphotericin B and application of a mucosal-to-serosal K+ gradient. This K+ current could be dose dependently depressed by the K+ channel blocker quinidine. Fluctuation analysis of the short-circuit current revealed a spontaneous and a blocker-induced Lorentzian noise component in the power density spectra. The Lorentzian corner frequencies increased linearly with the applied blocker concentration. This enabled the calculation of single K+ channel current and K+ channel density. Single K+ channel current was not affected by stimulation, whereas the number of quinidine-sensitive K+ channels in the basolateral membrane increased from 11 to 26.10(6).cm-2 in parallel to the hormonal stimulation transepithelial Na+ transport. This suggests that the basolateral membrane is a physiological target during synergistic aldosterone and thyroxine regulation of transepithelial Na+ transport for maintaining intracellular K+ homeostasis.
authors.affiliation: Institut für Tierphysiologie, Justus-Liebig-Universität, Giessen, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Illek
authors.forename: H
authors.initials: H
authors.lastname: Fischer
authors.forename: W
authors.initials: W
authors.lastname: Clauss
mesh_terms: D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D002642:Chick Embryo; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D007420:Intestine, Large / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011802:Quinidine / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013974:Thyroxine / Q000494:pharmacology
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D000450:Aldosterone; D012964:Sodium; D011802:Quinidine; D013974:Thyroxine