Potential identification of the O2-sensitive K+ current in a human neuroepithelial body-derived cell line.
Whole cell recording of H-146 cells revealed that the outward K+ current was completely inhibited by quinidine (IC50 approximately 17 microM). In contrast, maximal concentrations of 4-aminopyridine (4-AP; >/=10 mM) reversibly blocked only approximately 60% (IC50 approximately 1.52 mM). Ten millimolar 4-AP had no effect on the inhibition by hypoxia, which reduced current density from approximately 27 to approximately 13 pA/pF, whereas 1 mM quinidine abolished the hypoxic effect. In current clamp, 10 mM 4-AP depolarized the cell by approximately 18 mV and hypoxia caused further reversible depolarization of approximately 4 mV. One millimolar quinidine collapsed the membrane potential and abrogated any further hypoxic depolarization. RT-PCR revealed expression of the acid-sensitive, twin P domain K+ channel TASK but not of TWIK, TREK, or the known hypoxia-sensitive Kv2.1, which was confirmed by sequencing and further PCR with primers to the coding region of TASK. However, a reduction in extracellular pH had no effect on K+ current. Thus, although the current more closely resembles TWIK than TASK pharmacologically, structurally the reverse appears to be true. This suggests that a novel acid-insensitive channel related to TASK may be responsible for the hypoxia-sensitive K+ current of these cells.
O'Kelly
I
I
School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
Stephens
R H
RH
Peers
C
C
Kemp
P J
PJ
D001483:Base Sequence / Q000235:genetics; D018288:Carcinoma, Small Cell / Q000503:physiopathology; D002628:Chemoreceptor Cells / Q000502:physiology*; D004553:Electric Conductivity; D004848:Epithelium / Q000294:innervation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology; D008168:Lung / Q000294:innervation*; D008175:Lung Neoplasms / Q000503:physiopathology; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D015221:Potassium Channels; D010100:Oxygen