Two novel cardiac atrial K+ channels, IK.AA and IK.PC.
Two K(+)-selective channels in neonatal rat atrial cells activated by lipophilic compounds have been characterized in detail. The arachidonic acid-stimulated channel (IK.AA) had a slope conductance of 124 +/- 17 pS at +30 mV in symmetrical 140 mM potassium and a mean open time of approximately 1 ms, and was relatively voltage independent. IK.AA activity was reversibly increased by lowering pH to 6.0. Arachidonic acid was most effective in activating this channel, although a number of lipophilic compounds resulted in activation. Surprisingly, choline, a polar molecule, also activated the channel. A second K+ channel was activated by 10 microM phosphatidylcholine applied to the intracellular surface of inside-out atrial patches. This channel (IK.PC) had a slope conductance of 60 +/- 6 pS at +40 mV and a mean open time of approximately 0.6 ms, and was also relatively voltage independent. Fatty acids are probably monomeric in the membrane under the conditions of our recording; thus detergent effects are unlikely. Since a number of compounds including fatty acids and prostaglandins activated these two channels, an indirect, channel-specific mechanism may account for activation of these two cardiac K+ channels.
Wallert
M A
MA
Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905.
Ackerman
M J
MJ
Kim
D
D
Clapham
D E
DE
D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D016275:Atrial Function; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity / Q000187:drug effects / Q000502:physiology; D005227:Fatty Acids / Q000494:pharmacology; D006325:Heart Atria / Q000166:cytology / Q000648:ultrastructure; D010713:Phosphatidylcholines / Q000494:pharmacology; D011188:Potassium / Q000493:pharmacokinetics; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D011453:Prostaglandins / Q000494:pharmacology; D051381:Rats
D005227:Fatty Acids; D010713:Phosphatidylcholines; D015221:Potassium Channels; D011453:Prostaglandins; D016718:Arachidonic Acid; D011188:Potassium