Expression and function of the K+ channel KCNQ genes in human arteries.
OBJECTIVE
KCNQ-encoded voltage-gated potassium channels (K(v) 7) have recently been identified as important anti-constrictor elements in rodent blood vessels but the role of these channels and the effects of their modulation in human arteries remain unknown. Here, we have assessed KCNQ gene expression and function in human arteries ex vivo.


METHODS
Fifty arteries (41 from visceral adipose tissue, 9 mesenteric arteries) were obtained from subjects undergoing elective surgery. Quantitative RT-PCR experiments using primers specific for all known KCNQ genes and immunohistochemsitry were used to show K(v) 7 channel expression. Wire myography and single cell electrophysiology assessed the function of these channels.


RESULTS
KCNQ4 was expressed in all arteries assessed, with variable contributions from KCNQ1, 3 and 5. KCNQ2 was not detected. K(v) 7 channel isoform-dependent staining was revealed in the smooth muscle layer. In functional studies, the K(v) 7 channel blockers, XE991 and linopirdine increased isometric tension and inhibited K(+) currents. In contrast, the K(v) 7.1-specific blocker chromanol 293B did not affect vascular tone. Two K(v) 7 channel activators, retigabine and acrylamide S-1, relaxed preconstricted arteries, actions reversed by XE991. K(v) 7 channel activators also suppressed spontaneous contractile activity in seven arteries, reversible by XE991.


CONCLUSIONS
This is the first study to demonstrate not only the presence of KCNQ gene products in human arteries but also their contribution to vascular tone ex vivo.


BACKGROUND
This article is commented on by Mani and Byron, pp. 38-41 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2010.01065.x.
Ng
Fu Liang
FL
Biomedical Sciences, Ion Channels and Cell Signalling, St. George's, University of London, London, UK.
Davis
Alison J
AJ
Jepps
Thomas A
TA
Harhun
Maksym I
MI
Yeung
Shuk Yin
SY
Wan
Andrew
A
Reddy
Marcus
M
Melville
David
D
Nardi
Antonio
A
Khong
Teck K
TK
Greenwood
Iain A
IA
D000368:Aged; D001158:Arteries / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D051656:KCNQ Potassium Channels / Q000187:drug effects / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics
D051656:KCNQ Potassium Channels; D012333:RNA, Messenger