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An oxygen‐, acid‐ and anaesthetic‐sensitive TASK‐like background potassium channel in rat arterial chemoreceptor cells
Author(s) -
Buckler Keith J.,
Williams Beatrice A.,
Honore Eric
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00135.x
Subject(s) - carotid body , potassium channel , quinidine , membrane potential , halothane , biophysics , chemistry , patch clamp , electrophysiology , oxygen , anesthesia , biochemistry , pharmacology , medicine , biology , receptor , organic chemistry
1 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. 2 Under symmetrical K + conditions the oxygen‐sensitive whole cell K + current had a linear dependence on voltage indicating a lack of intrinsic voltage sensitivity. 3 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. 4 Oxygen‐sensitive current was inhibited by 10 mM barium (57 % inhibition), 200 μM zinc (53 % inhibition), 200 μM bupivacaine (55 % inhibition) and 1 mM quinidine (105 % inhibition). 5 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. 6 Acidosis (pH 6.4) inhibited the oxygen‐sensitive background K + current (by 56 %) and depolarised type‐I cells. 7 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.