An oxygen-, acid- and anaesthetic-sensitive TASK-like background potassium channel in rat arterial chemoreceptor cells

• Published in: The Journal of physiology 2000-05, Vol.525 (1), p.135-142
• Main Authors: Buckler, Keith J., Williams, Beatrice A., Honore, Eric
• Format: Article
• Language: English
• Subjects: Acidosis; Anesthetics - pharmacology; Animals; Barium - pharmacology; Bupivacaine - pharmacology; Carotid Arteries - metabolism; Cells, Cultured; Chemoreceptor Cells - metabolism; Halothane - pharmacology; Hydrogen-Ion Concentration; In Situ Hybridization; Oxygen - pharmacology; Patch-Clamp Techniques; Potassium Channels - metabolism; Potassium Channels, Tandem Pore Domain; Quinidine - pharmacology; Rapid Report; Rats; Rats, Sprague-Dawley; RNA, Messenger - metabolism; Zinc - pharmacology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.2000.00135.x

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 μM zinc (53 % inhibition), 200 μM 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.