A novel cardiac potassium channel that is active and conductive at depolarized potentials

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Abstract
We report the existence of a novel potassium channel revealed in single-channel recordings from guinea-pig ventricular heart cells. The channel, observed in ∼10% of patches, demonstrates a 14 pS conductance at physiological potassium concentrations, does not rectify over the voltage range of the action potential, and is quite selective for K ions. The channel activates with depolarization, but does not require intracellular Ca2+ ions to open. Open channel probability increases rapidly (600 ms). These features clearly distinguish this channel from other known K channels in cardiac muscle. Because of its high activity at plateau potentials, we propose the namei Kp.