An oxygen-, acid- and anaesthetic-sensitive TASK-like background potassium channel in rat arterial chemoreceptor cells.
The biophysical and pharmacological properties of an oxygen-sensitive background K+ current in rat carotid body type-I cells were investigated and compared with those of recently cloned two pore domain K+ channels. Under symmetrical K+ conditions the oxygen-sensitive whole cell K+ current had a linear dependence on voltage indicating a lack of intrinsic voltage sensitivity. Single channel recordings identified a K+ channel, open at resting membrane potentials, that was inhibited by hypoxia. This channel had a single channel conductance of 14 pS, flickery kinetics and showed little voltage sensitivity except at extreme positive potentials. Oxygen-sensitive current was inhibited by 10 mM barium (57% inhibition), 200 microM zinc (53% inhibition), 200 microM bupivacaine (55% inhibition) and 1 mM quinidine (105 % inhibition). The general anaesthetic halothane (1.5%) increased the oxygen-sensitive K+ current (by 176%). Halothane (3 mM) also stimulated single channel activity in inside-out patches (by 240%). Chloroform had no effect on background K+ channel activity. Acidosis (pH 6.4) inhibited the oxygen-sensitive background K+ current (by 56%) and depolarised type-I cells. The pharmacological and biophysical properties of the background K+ channel are, therefore, analogous to those of the cloned channel TASK-1. Using in situ hybridisation TASK-1 mRNA was found to be expressed in type-I cells. We conclude that the oxygen- and acid-sensitive background K+ channel of carotid body type-I cells is likely to be an endogenous TASK-1-like channel.
Buckler
K J
KJ
University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK. keith.buckler@physiol.ox.ac.uk
Williams
B A
BA
Honore
E
E
D000138:Acidosis; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002045:Bupivacaine / Q000494:pharmacology; D002339:Carotid Arteries / Q000378:metabolism*; D002478:Cells, Cultured; D002628:Chemoreceptor Cells / Q000378:metabolism*; D006221:Halothane / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D017403:In Situ Hybridization; D009419:Nerve Tissue Proteins; D010100:Oxygen / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D024683:Potassium Channels, Tandem Pore Domain; D011802:Quinidine / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015032:Zinc / Q000494:pharmacology
D000777:Anesthetics; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger; C420132:potassium channel subfamily K member 3; D001464:Barium; D011802:Quinidine; D015032:Zinc; D010100:Oxygen; D006221:Halothane; D002045:Bupivacaine