title: Characterization of slowly inactivating KV{alpha} current in rabbit pulmonary neuroepithelial bodies: effects of hypoxia and nicotine.
abstract: Pulmonary neuroepithelial bodies (NEB) form innervated cell clusters that express voltage-activated currents and function as airway O(2) sensors. We investigated A-type K(+) currents in NEB cells using neonatal rabbit lung slice preparation. The whole cell K(+) current was slowly inactivating with activation threshold of approximately -30 mV. This current was blocked approximately 27% by blood-depressing substance I (BDS-I; 3 microM), a selective blocker of Kv3.4 subunit, and reduced approximately 20% by tetraethylammonium (TEA; 100 microM). The BDS-I-sensitive component had an average peak value of 189 +/- 14 pA and showed fast inactivation kinetics that could be fitted by one-component exponential function with a time constant of (tau1) 77 +/- 10 ms. This Kv slowly inactivating current was also blocked by heteropodatoxin-2 (HpTx-2; 0.2 microM), a blocker of Kv4 subunit. The HpTx-2-sensitive current had an average peak value of 234 +/- 23 pA with a time constant (tau) 82 +/- 11 ms. Hypoxia (Po(2) = 15-20 mmHg) inhibited the slowly inactivating K(+) current by approximately 47%, during voltage steps from -30 to +30 mV, and no further inhibition occurred when TEA was combined with hypoxia. Nicotine at concentrations of 50 and 100 microM suppressed the slowly inactivating K(+) current by approximately 24 and approximately 40%, respectively. This suppression was not reversed by mecamylamine suggesting a direct effect of nicotine on these K(+) channels. In situ hybridization experiments detected expression of mRNAs for Kv3.4 and Kv4.3 subunits, while double-label immunofluorescence confirmed membrane localization of respective channel proteins in NEB cells. These studies suggest that the hypoxia-sensitive current in NEB cells is carried by slowly inactivating A-type K(+) channels, which underlie their oxygen-sensitive potassium currents, and that exposure to nicotine may directly affect their function, contributing to smoking-related lung disease.
authors.affiliation: Division of Pathology, Department of Pediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and University of Toronto, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Xiao Wen
authors.initials: XW
authors.lastname: Fu
authors.forename: Colin
authors.initials: C
authors.lastname: Nurse
authors.forename: Ernest
authors.initials: E
authors.lastname: Cutz
mesh_terms: D000818:Animals; D003064:Cnidarian Venoms / Q000494:pharmacology; D004553:Electric Conductivity; D005260:Female; D005455:Fluorescent Antibody Technique; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D066298:In Vitro Techniques; D008168:Lung / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D046568:Neuroepithelial Bodies / Q000378:metabolism*; D009538:Nicotine / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D051672:Shal Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051670:Shaw Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013111:Spider Venoms / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D014018:Tissue Distribution
chemical_list: C059796:BDS-I antiviral protein, Anemonia sulcata; D003064:Cnidarian Venoms; C524386:HpTx-2 protein, Heteropoda venatoria; D026902:Potassium Channel Blockers; D012333:RNA, Messenger; D051672:Shal Potassium Channels; D051670:Shaw Potassium Channels; D013111:Spider Venoms; D019789:Tetraethylammonium; D009538:Nicotine