| 11483700 |
Cheong A, Dedman AM, Beech DJ: Expression and function of native potassium channel [K (V) alpha1] subunits in terminal arterioles of rabbit. J Physiol. 2001 Aug 1;534(Pt 3):691-700.
1. In this study we investigated the expression and function of the K (V) alpha1 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) alpha1 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 nM endothelin-1 constricted further in response to 3,4-DAP, 4-AP or correolide, but not to rAgTX2. 6. We suggest that K (V) alpha1 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) alpha1 complexes without K (V) 1.5 appear to be uncommon. |
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