title: Influence of permeating ions on potassium channel block by external tetraethylammonium.
abstract: 1. Block by external tetraethylammonium (TEA) was examined on currents carried by potassium (K+) and sodium (Na+) through the cloned delayed rectifier K+ channel Kv2.1. 2. In the presence of high intracellular K+ and high extracellular Na+, currents through the Kv2.1 channel were carried almost exclusively by K+. In the absence of both intracellular and extracellular K+, large currents were carried by Na+ through the Kv2.1 channel. 3. External application of 30 mM TEA blocked K+ currents through Kv2.1 by 87%. The same external concentration of TEA had no effect on Na+ currents through this channel. 4. As the K+ concentration was increased between 0 and 140 mM, the percentage of current blocked by TEA progressively increased from 0 to 87%. 5. These data indicate that block of K+ channels by external TEA depends on the permeating ion. Furthermore, these data indicate that in the presence of Na+ and absence of K+, TEA does not bind to the channel, and that addition of low concentrations of K+ facilitates TEA binding.
mesh_terms: D000818:Animals; D002460:Cell Line; D004553:Electric Conductivity; D006801:Humans; D007477:Ions; D051379:Mice; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D010539:Permeability; D011188:Potassium / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D012964:Sodium / Q000502:physiology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
chemical_list: D007477:Ions; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D012964:Sodium; D011188:Potassium