Three Types of Single Voltage-Dependent Potassium Channels in the Sarcolemma of Frog Skeletal Muscle

Three Types of Single Voltage-Dependent Potassium Channels in the Sarcolemma of Frog Skeletal Muscle Patch-clamp experiments in the sarcolemma of frog skeletal muscle evidenced the presence of three types of voltage-dependent single-channel K+ currents. According to their unitary conductance at a membrane voltage of +40 mV, we classified them as 16-, 13-, and 7-pS K+ channels. The 16-pS K+ channels are active close to a membrane voltage of −80 mV and they do not become inactivated during voltage pulses of 100 ms. Within 10 min after beginning the recording, these channels developed rundown with an exponential time course. The 13-pS K+ channels are active near −60 mV; upon a 100-ms depolarization, they exhibited inactivation with an approximate exponential time course. The 7-pS K+ channels were recorded at voltages positive to 0 mV. In patches containing all three types of K+ channels, the ensemble average currents resemble the kinetic properties of the macroscopic delayed rectifier K+ currents recorded in skeletal muscle and other tissues. In conclusion, the biophysical properties of unitary K+ currents suggest that these single-channel K+ currents may underlie the macroscopic delayed K+ currents in frog skeletal muscle fibers. In addition, since the 16- and 13-pS channels were more frequently recorded, both are the main contributors to the delayed K+ currents. The Journal of Membrane Biology Springer Journals

Three Types of Single Voltage-Dependent Potassium Channels in the Sarcolemma of Frog Skeletal Muscle

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Copyright © 2009 by Springer Science+Business Media, LLC
Life Sciences; Human Physiology ; Biochemistry, general
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