title: Electrolyte transport in the mouse trachea: no evidence for a contribution of luminal K(+) conductance.
abstract: Recent studies on frog skin acini have challenged the question whether Cl(-) secretion or Na(+) absorption in the airways is driven by luminal K(+) channels in series to a basolateral K(+) conductance. We examined the possible role of luminal K(+) channels in electrolyte transport in mouse trachea in Ussing-chamber experiments. Tracheas of both normal and CFTR (-/-) mice showed a dominant amiloride-sensitive Na+ absorption under both, control conditions and after cAMP-dependent stimulation. The lumen-negative transepithelial voltage was enhanced after application of IBMX and forskolin and Cl(-) secretion was activated. Electrolyte secretion induced by IBMX and forskolin was inhibited by luminal glibenclamide and the blocker of basolateral Na(+2)Cl(-)K(+) cotransporter azosemide. Similarly, the compound 293B, a blocker of basolateral KCNQ1/KCNE3 K(+) channels effectively blocked Cl(-) secretion when applied to either the luminal or basolateral side of the epithelium. RT-PCR analysis suggested expression of additional K(+) channels in tracheal epithelial cells such as Slo1 and Kir6.2. However, we did not detect any functional evidence for expression of luminal K(+) channels in mouse airways, using luminal 293B, clotrimazole and Ba(2+) or different K(+) channel toxins such as charybdotoxin, apamin and a-dendrotoxin. Thus, the present study demonstrates Cl(-) secretion in mouse airways, which depends on basolateral Na(+2)Cl(-)K(+) cotransport and luminal CFTR and non-CFTR Cl(-) channels. Cl(-) secretion is maintained by the activity of basolateral K(+) channels, while no clear evidence was found for the presence of a luminal K(+) conductance.
authors.affiliation: Department of Physiology & Pharmacology, University of Queensland, St. Lucia, QLD 4072, Brisbane, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Schreiber
authors.forename: B
authors.initials: B
authors.lastname: Mürle
authors.forename: J
authors.initials: J
authors.lastname: Sun
authors.forename: K
authors.initials: K
authors.lastname: Kunzelmann
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D026902:Potassium Channel Blockers / Q000378:metabolism / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D012680:Sensitivity and Specificity; D014132:Trachea / Q000187:drug effects / Q000502:physiology*
chemical_list: D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels