Activation of Ca2+-dependent K+ channels by cyanide in guinea pig adrenal chromaffin cells |
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Authors: | Inoue, M. Imanaga, I. |
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Abstract: | The effects ofcyanide (CN) on whole cell current measured with the perforated-patchmethod were studied in adrenal medullary cells. Application of CNproduced initially inward and then outward currents at 52 mV ormore negative. As the membrane potential was hyperpolarized, amplitudeand latency of the outward current (Io) by CNbecame small and long, respectively. A decrease in the externalNa+ concentration did not affectthe latency for CN-inducedIo but enhancedthe amplitude markedly. The CNIo reversedpolarity at 85 mV, close to the Nernst potential forK+, and was suppressed by theK+ channel blockers curare andapamin but not by glibenclamide, suggesting thatIo is due to theactivation of Ca2+-dependentK+ channels. Consistent with thisnotion, the Ca2+-mobilizingagents, muscarine and caffeine, also producedIo. Exposure toCN in a Ca2+-deficient medium for4 min abolished caffeine- or muscarine-induced Io withoutdevelopment ofIo, and additionof Ca2+ to the CN-containingsolution inducedIo. We concludethat exposure to CN producesCa2+-dependentK+ currents in an externalCa2+-dependent manner, probablyvia facilitation of Ca2+ influx. |
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