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Expression and function of native potassium channel (K V α1) subunits in terminal arterioles of rabbit
Author(s) -
Cheong A.,
Dedman A. M.,
Beech D. J.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00691.x
Subject(s) - rabbit (cipher) , potassium channel , terminal (telecommunication) , potassium , biophysics , chemistry , function (biology) , potassium channel blocker , protein subunit , microbiology and biotechnology , biochemistry , biology , gene , computer science , telecommunications , computer security , organic chemistry
1 In this study we investigated the expression and function of the K V α1 subfamily of voltage‐gated K + channels in terminal arterioles from rabbit cerebral circulation. 2 K + current was measured from smooth muscle cells within intact freshly isolated arteriolar fragments. Current activated on depolarisation positive of about –45 mV and a large fraction of this current was blocked by 3,4‐diaminopyridine (3,4‐DAP) or 4‐aminopyridine (4‐AP), inhibitors of K V channels. Expression of cRNA encoding K V 1.6 in Xenopus oocytes also generated a 4‐AP‐sensitive K + current with a threshold for activation near –45 mV. 3 Immunofluorescence labelling revealed K V 1.2 to be specifically localised to endothelial cells, and K V 1.5 and K V 1.6 to plasma membranes of smooth muscle cells. 4 K V channel current in arteriolar fragments was blocked by correolide (which is specific for the K V α1 family of K V channels) but was resistant to recombinant agitoxin‐2 (rAgTX2; which inhibits K V 1.6 but not K V 1.5). Heterologously expressed K V 2.1 was resistant to correolide, and K V 1.6 was blocked by rAgTX2. 5 Arterioles that were mildly preconstricted and depolarised by 0.1–0.3 n m endothelin‐1 constricted further in response to 3,4‐DAP, 4‐AP or correolide, but not to rAgTX2. 6 We suggest that K V α1 channels are expressed in smooth muscle cells of terminal arterioles, underlie a major part of the voltage‐dependent K + current, and have a physiological function to oppose vasoconstriction. K V α1 complexes without K V 1.5 appear to be uncommon.