Inward-rectifier potassium channel: Difference between revisions

By convention, inward current (positive charge moving into the cell) is displayed in [[voltage clamp]] as a downward deflection, while an outward current (positive charge moving out of the cell) is shown as an upward deflection. At membrane potentials negative to potassium's [[reversal potential]], inwardly rectifying K⁺ channels support the flow of positively charged K⁺ ions into the cell, pushing the membrane potential back to the resting potential. This can be seen in figure 1: when the membrane potential is clamped negative to the channel's resting potential (e.g. -60 mV), inward current flows (i.e. positive charge flows into the cell). However, when the membrane potential is set positive to the channel's resting potential (e.g. +60 mV), these channels pass very little current. Simply put, this channel passes much more current in the inward direction than the outward one, at its operating voltage range. These channels are not perfect rectifiers, as they can pass some outward current in the voltage range up to about 30 mV above resting potential.

 

 

Inward rectifiers also differ from [[tandem pore domain potassium channel]]s, which are largely responsible for "leak" K⁺ currents.<ref>Hille, p. 155.</ref> Some inward rectifiers, termed "weak inward rectifiers", carry measurable outward K⁺ currents at voltages positive to the K⁺ reversal potential (corresponding to, but larger than, the small currents above the 0 nA line in figure 1). They, along with the "leak" channels, establish the resting membrane potential of the cell. Other inwardly rectifying channels, termed "strong inward rectifiers," carry very little outward current at all, and are mainly active at voltages negative to the K⁺ reversal potential, where they carry inward current (the much larger currents below the 0 nA line in figure 1).<ref>Hille, p. 153.</ref>

 

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