Killing K channels with TEA+.
Tetraethylammonium (TEA+) is widely used for reversible blockade of K channels in many preparations. We noticed that intracellular perfusion of voltage-clamped squid giant axons with a solution containing K+ and TEA+ irreversibly decreased the potassium current when there was no K+ outside. Five minutes of perfusion with 20 mM TEA+, followed by removal of TEA+, reduced potassium current to < 5% of its initial value. The irreversible disappearance of K channels with TEA+ could be prevented by addition of > or = 10 mM K+ to the extracellular solution. The rate of disappearance of K channels followed first-order kinetics and was slowed by reducing the concentration of TEA+. Killing is much less evident when an axon is held at -110 mV to tightly close all of the channels. The longer-chain TEA+ derivative decyltriethylammonium (C10+) had irreversible effects similar to TEA+. External K+ also protected K channels against the irreversible action of C10+. It has been reported that removal of all K+ internally and externally (dekalification) can result in the disappearance of K channels, suggesting that binding of K+ within the pore is required to maintain function. Our evidence further suggests that the crucial location for K+ binding is external to the (internal) TEA+ site and that TEA+ prevents refilling of this location by intracellular K+. Thus in the absence of extracellular K+, application of TEA+ (or C10+) has effects resembling dekalification and kills the K channels.
Khodakhah
K
K
Department of Physiology, University of Pennsylvania, Philadelphia 19104, USA.
Melishchuk
A
A
Armstrong
C M
CM
D001665:Binding Sites; D017136:Ion Transport; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D019789:Tetraethylammonium / Q000378:metabolism / Q000494:pharmacology*
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D019789:Tetraethylammonium; D011188:Potassium