Reconstitution in lipid bilayers of an ATP-sensitive K+ channel from pig coronary smooth muscle.
A K+ channel with a main conductance of 29 pS was recorded after the incorporation of coronary artery membrane vesicles into lipid bilayers. This channel was identified as an ATP-sensitive K+ channel (KATP) because its activity was diminished by the internal application of 50-250 microM ATP-Na2. Moreover, it was opened when 10-50 microM pinacidil was externally applied. Single-channel records revealed the existence of several (sub)conductance states. At 0 mV and with a 5/250 KCl gradient, the main conductance of the KATP channel was 29 pS. The other (sub)conductance states were less frequent and had discrete values of 12, 17 and 22 pS. Pinacidil stabilized the channel open state primarily in the 29 pS conductance level; whereas ATP inhibited all the conductance levels. In general, KATP channels were characterized by brief openings followed by long closings (open probability, Po approximately 0.02); only occasionally (3 out of 12 experiments) did the KATP channels have a high open probability (Po >/= 0.7). Channel activity could be increased or rescued by adding 2.5-10 mM UDP-TRIS and 0.5-2 mM MgCl2 to the internal side of the channel.
Ottolia
M
M
Department of Anesthesiology, BH-612 CHS, University of California at Los Angeles, CA 90095, USA.
Toro
L
L
D000255:Adenosine Triphosphate; D000818:Animals; D003331:Coronary Vessels / Q000502:physiology*; D004594:Electrophysiology; D008051:Lipid Bilayers; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D013552:Swine
D008051:Lipid Bilayers; D015221:Potassium Channels; D000255:Adenosine Triphosphate