Molecular expression and pharmacological identification of a role for K(v)7 channels in murine vascular reactivity.
OBJECTIVE
This study represents a novel characterisation of KCNQ-encoded potassium channels in the vasculature using a variety of pharmacological and molecular tools to determine their role in contractility.


METHODS
Reverse transcriptase polymerase chain reaction (RT-PCR) experiments were undertaken on RNA isolated from mouse aorta, carotid artery, femoral artery and mesenteric artery using primers specific for all known KCNQ genes. RNA isolated from mouse heart and brain were used as positive controls. Pharmacological experiments were undertaken on segments from the same blood vessels to determine channel functionality. Immunocytochemical experiments were performed on isolated myocytes from thoracic aorta.


RESULTS
All blood vessels expressed KCNQ1, 4 and 5 with hitherto 'neuronal' KCNQ4 being, surprisingly, the most abundant. The correlated proteins K(v)7.1, K(v)7.4 and K(v)7.5 were identified in the cell membranes of aortic myocytes by immunocytochemistry. Application of three compounds known to activate K(v)7 channels, retigabine (2 -20 microM), flupirtine (20 microM) and meclofenamic acid (20 microM), relaxed vessels precontracted by phenylephrine or 1 mM 4-aminopyridine but had no effect on contractions produced by 60 mM KCl or the K(v)7 channel blocker XE991 (10 microM). All vessels tested contracted upon application of the K(v)7 channel blockers XE991 and linopirdine (0.1-10 microM).


CONCLUSIONS
Murine blood vessels exhibit a distinctive KCNQ expression profile with 'neuronal' KCNQ4 dominating. The ion channels encoded by KCNQ genes have a crucial role in defining vascular reactivity as K(v)7 channel blockers produced marked contractions whereas K(v)7 channel activators were effective vasorelaxants.
Yeung
S Y M
SY
Division of Basic Medical Sciences, Ion Channels and Cell Signalling Research Centre, St George's, University of London, London, UK.
Pucovský
V
V
Moffatt
J D
JD
Saldanha
L
L
Schwake
M
M
Ohya
S
S
Greenwood
I A
IA
D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D002219:Carbamates / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020869:Gene Expression Profiling; D007150:Immunohistochemistry; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology; D007537:Isometric Contraction; D051656:KCNQ Potassium Channels / Q000378:metabolism*; D051657:KCNQ1 Potassium Channel / Q000378:metabolism*; D008469:Meclofenamic Acid / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D010655:Phenylenediamines / Q000008:administration & dosage / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000819:agonists; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000631:Aminopyridines; D000873:Anthracenes; D002219:Carbamates; D007211:Indoles; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C506326:KCNQ5 channel, mouse; C496910:Kcnq1 protein, mouse; C492167:Kcnq4 protein, mouse; D010655:Phenylenediamines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011725:Pyridines; C101866:ezogabine; D008469:Meclofenamic Acid; D012313:RNA; C061017:linopirdine; C034161:flupirtine