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Am J Physiol Heart Circ Physiol 291: H770-H780, 2006. First published March 24, 2006; doi:10.1152/ajpheart.01377.2005
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Evidence for two-pore domain potassium channels in rat cerebral arteries

Robert M. Bryan, Jr.,1,2,3 Junping You,1 Sharon C. Phillips,1 Jon J. Andresen,1 Eric E. Lloyd,1 Paul A. Rogers,4 Stuart E. Dryer,5 and Sean P. Marrelli1,3

Departments of 1Anesthesiology, 2Medicine (Cardiovascular Sciences), and 3Molecular Physiology and Biophysics, Baylor College of Medicine, 5Department of Biochemistry and Biological Sciences, University of Houston, Houston, Texas; and 4Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, Louisiana

Submitted 28 December 2005 ; accepted in final form 7 March 2006

Little is known about the presence and function of two-pore domain K+ (K2P) channels in vascular smooth muscle cells (VSMCs). Five members of the K2P channel family are known to be directly activated by arachidonic acid (AA). The purpose of this study was to determine 1) whether AA-sensitive K2P 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 K2P 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 µM) 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 µM glibenclamide, or 100 µM Ba2+. AA-induced dilations were blocked by 50 mM K+, indicating involvement of a K+ channel. AA (10 µM) 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 K2P channel family.

arachidonic acid; arachidonic acid-stimulated potassium channel; membrane potential; hyperpolarization; vasodilation; electrophysiology; TREK-1; TREK-2; TRAAK; THIK-1; TWIK-2


Address for reprint requests and other correspondence: R. M. Bryan, Jr., Dept. of Anesthesiology 434D, One Baylor Plaza, Houston, TX 77030 (e-mail: rbryan{at}bcm.tmc.edu)




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