Bryan Robert M, You Junping, Phillips Sharon C, Andresen Jon J, Lloyd Eric E, Rogers Paul A, Dryer Stuart E, Marrelli Sean P
Department of Anesthesiology, Baylor College of Medicine, University of Houston, Houston, Texas 77030, USA.
Am J Physiol Heart Circ Physiol. 2006 Aug;291(2):H770-80. doi: 10.1152/ajpheart.01377.2005. Epub 2006 Mar 24.
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.
关于双孔结构域钾离子（K(2P)）通道在血管平滑肌细胞（VSMC）中的存在情况及功能，目前所知甚少。已知K(2P)通道家族的五个成员可被花生四烯酸（AA）直接激活。本研究的目的是确定：1）AA敏感的K(2P)通道是否在脑VSMC中表达；2）AA是否通过非典型钾离子通道增加VSMC中的钾离子电流来舒张大鼠大脑中动脉（MCA）。逆转录聚合酶链反应（RT-PCR）显示，在大鼠MCA中存在以下AA敏感的K(2P)通道的信息：内向整流钾离子通道P结构域串联体（TWIK-2）、TWIK相关钾离子通道（TREK-1和TREK-2）、TWIK相关AA刺激钾离子通道（TRAAK）以及TWIK相关氟烷抑制钾离子通道（THIK-1）。然而，在分离的VSMC中，仅发现了TWIK-2的信息。蛋白质免疫印迹法显示TWIK-2存在于MCA中，免疫组织化学进一步证实其在VSMC中的存在。AA（10 - 100微摩尔）通过一种不依赖内皮的机制舒张MCA。AA诱导的舒张不受环氧化酶、环氧合酶或脂氧合酶抑制的影响，也不受10毫摩尔四乙铵（TEA）、3毫摩尔4-氨基吡啶、10微摩尔格列本脲或100微摩尔钡离子（Ba2+）对经典钾离子通道抑制的影响。50毫摩尔钾离子可阻断AA诱导的舒张，表明涉及钾离子通道。AA（10微摩尔）增加了分散的脑VSMC中的全细胞钾离子电流。AA诱导的电流不受AA代谢途径抑制剂或经典钾离子通道阻断的影响。我们得出结论，AA通过一种可能是K(2P)通道家族成员的非典型钾离子通道舒张大鼠MCA并增加VSMC中的钾离子电流。
