A Ba2+-resistant, acid-sensitive K+ conductance in Na+-absorbing H441 human airway epithelial cells.
By analysis of whole cell membrane currents in Na(+)-absorbing H441 human airway epithelial cells, we have identified a K(+) conductance (G(K)) resistant to Ba(2+) but sensitive to bupivacaine or extracellular acidification. In polarized H441 monolayers, we have demonstrated that bupivacaine, lidocaine, and quinidine inhibit basolateral membrane K(+) current (I(Bl)) whereas Ba(2+) has only a weak inhibitory effect. I(Bl) was also inhibited by basolateral acidification, and, although subsequent addition of bupivacaine caused a further fall in I(Bl), acidification had no effect after bupivacaine, demonstrating that cells grown under these conditions express at least two different bupivacaine-sensitive K(+) channels, only one of which is acid sensitive. Basolateral acidification also inhibited short-circuit current (I(SC)), and basolateral bupivacaine, lidocaine, quinidine, and Ba(2+) inhibited I(SC) at concentrations similar to those needed to inhibit I(Bl), suggesting that the K(+) channels underlying I(Bl) are part of the absorptive mechanism. Analyses using RT-PCR showed that mRNA encoding several two-pore domain K(+) (K2P) channels was detected in cells grown under standard conditions (TWIK-1, TREK-1, TASK-2, TWIK-2, KCNK-7, TASK-3, TREK-2, THIK-1, and TALK-2). We therefore suggest that K2P channels underlie G(K) in unstimulated cells and so maintain the driving force for Na(+) absorption. Since this ion transport process is vital to lung function, K2P channels thus play an important but previously undocumented role in pulmonary physiology.
Inglis
Sarah K
SK
Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland.
Brown
Sean G
SG
Constable
Maree J
MJ
McTavish
Niall
N
Olver
Richard E
RE
Wilson
Stuart M
SM
D001464:Barium / Q000494:pharmacology*; D002045:Bupivacaine / Q000494:pharmacology; D002460:Cell Line; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D020545:Respiratory Mucosa / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*
D015221:Potassium Channels; D001464:Barium; D012313:RNA; D012964:Sodium; D002045:Bupivacaine