What question did this study set out to answer?

Investigate the mechanism causing the decrease in resting potassium permeability under extreme membrane hyperpolarization in skeletal muscle fibres.

September 1, 1979The Journal of PhysiologyOpen Access

Potassium depletion and sodium block of potassium currents under hyperpolarization in frog sartorius muscle.

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Authors

NSN. B. StandenLa Trobe University PSPeter StanfieldGoogle (United States)

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Implication

Voltage-clamp study reveals that hyperpolarization-induced decreases in muscle potassium currents stem from external sodium block and tubular depletion, highlighting distinct gating mechanisms.

Key Points

Investigate the mechanism causing the decrease in resting potassium permeability under extreme membrane hyperpolarization in skeletal muscle fibres.
Applied a three-electrode voltage clamp technique to frog sartorius muscle fibres across membrane potentials ranging down to -240 mV.
Manipulated extracellular sodium concentration from 14 to 140 mM and substituted sodium with TMA, Tris, or lithium to analyze ionic block and recovery kinetics.
Formulated a three-compartment mathematical model to simulate the time course of potassium depletion from the transverse tubular system lumen.
External sodium produced a voltage-dependent block of inward potassium currents beyond -140 mV, yielding a negative-slope current-voltage relationship that was abolished by substituting sodium with TMA, Tris, or lithium.
Increasing external sodium from 70 to 140 mM accelerated the current turn-off rate (tau) across hyperpolarized potentials and shifted the negative-slope region toward less negative voltages.
Post-hyperpolarization recovery in 70 mM sodium was approximately 9 times faster following a step to -210 mV compared to -120 mV, confirming tubular potassium depletion dominates at -120 mV whereas sodium block dominates at extreme hyperpolarization.

Cite This Study

Standen et al. (1979) studied this question.

synapsesocial.com/papers/6a766d0146f688d752c442f7 https://doi.org/10.1113/jphysiol.1979.sp012943

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Implication

Voltage-clamp study reveals that hyperpolarization-induced decreases in muscle potassium currents stem from external sodium block and tubular depletion, highlighting distinct gating mechanisms.

Potassium depletion and sodium block of potassium currents under hyperpolarization in frog sartorius muscle.

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Implication

Key Points

Cite This Study

Potassium depletion and sodium block of potassium currents under hyperpolarization in frog sartorius muscle.

Discussion

Member takes

Implication

Key Points

Cite This Study

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