Molecular expression and pharmacological identification of a role for Kv7 channels in murine vascular reactivity

Authors


Division Of Basic Medical Sciences, Ion Channels And Cell Signalling Research Centre, St George's University of London, Cranmer Terrace, London, SW17 0RE UK. E-mail: i.greenwood@sgul.ac.uk

Abstract

Background and purpose:

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.

Experimental approach:

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.

Key results:

All blood vessels expressed KCNQ1, 4 and 5 with hitherto ‘neuronal’ KCNQ4 being, surprisingly, the most abundant. The correlated proteins Kv7.1, Kv7.4 and Kv7.5 were identified in the cell membranes of aortic myocytes by immunocytochemistry. Application of three compounds known to activate Kv7 channels, retigabine (2 –20 μM), flupirtine (20 μM) and meclofenamic acid (20 μM), relaxed vessels precontracted by phenylephrine or 1 mM 4-aminopyridine but had no effect on contractions produced by 60 mM KCl or the Kv7 channel blocker XE991 (10 μM). All vessels tested contracted upon application of the Kv7 channel blockers XE991 and linopirdine (0.1-10 μM).

Conclusions and implications:

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 Kv7 channel blockers produced marked contractions whereas Kv7 channel activators were effective vasorelaxants.

British Journal of Pharmacology (2007) 151, 758–770; doi:10.1038/sj.bjp.0707284

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