Characterization of slowly inactivating KV{alpha} current in rabbit pulmonary neuroepithelial bodies: effects of hypoxia and nicotine.
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.
Fu
Xiao Wen
XW
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.
Nurse
Colin
C
Cutz
Ernest
E
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
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