Evidence for two-pore domain potassium channels in rat cerebral arteries.
Little is known about the presence and function of two-pore domain K(+) (K(2P)) channels in vascular smooth muscle cells (VSMCs). Five members of the K(2P) channel family are known to be directly activated by arachidonic acid (AA). The purpose of this study was to determine 1) whether AA-sensitive K(2P) channels are expressed in cerebral VSMCs and 2) whether AA dilates the rat middle cerebral artery (MCA) by increasing K+ currents in VSMCs via an atypical K+ channel. RT-PCR revealed message for the following AA-sensitive K(2P) channels in rat MCA: tandem of P domains in weak inward rectifier K+ (TWIK-2), TWIK-related K+ (TREK-1 and TREK-2), TWIK-related AA-stimulated K+ (TRAAK), and TWIK-related halothane-inhibited K+ (THIK-1) channels. However, in isolated VSMCs, only message for TWIK-2 was found. Western blotting showed that TWIK-2 is present in MCA, and immunohistochemistry further demonstrated its presence in VSMCs. AA (10-100 microM) dilated MCAs through an endothelium-independent mechanism. AA-induced dilation was not affected by inhibition of cyclooxygenase, epoxygenase, or lipoxygenase or inhibition of classical K+ channels with 10 mM TEA, 3 mM 4-aminopyridine, 10 microM glibenclamide, or 100 microM Ba2+. AA-induced dilations were blocked by 50 mM K+, indicating involvement of a K+ channel. AA (10 microM) increased whole cell K+ currents in dispersed cerebral VSMCs. AA-induced currents were not affected by inhibitors of the AA metabolic pathways or blockade of classical K+ channels. We conclude that AA dilates the rat MCA and increases K+ currents in VSMCs via an atypical K+ channel that is likely a member of the K(2P) channel family.
Department of Anesthesiology, Baylor College of Medicine, University of Houston, Houston, Texas 77030, USA. rbryan@bcm.tmc.edu
Robert M
RM
Bryan
Junping
J
You
Sharon C
SC
Phillips
Jon J
JJ
Andresen
Eric E
EE
Lloyd
Paul A
PA
Rogers
Stuart E
SE
Dryer
Sean P
SP
Marrelli
D000199:Actins / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D015153:Blotting, Western; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism*; D004594:Electrophysiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D024683:Potassium Channels, Tandem Pore Domain / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014664:Vasodilation / Q000187:drug effects
D000199:Actins; C503444:Kcnk10 protein, rat; C430725:Kcnk13 protein, rat; C503434:Kcnk4 protein, rat; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; C103742:potassium channel protein TREK-1; D016718:Arachidonic Acid