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Potassium conductance changes in skeletal muscle and the potassium concentration in the transverse tubules
Author(s) -
Almers W.
Publication year - 1972
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1972.sp009928
Subject(s) - hyperpolarization (physics) , membrane potential , chemistry , conductance , potassium , biophysics , sartorius muscle , resting potential , permeability (electromagnetism) , reversal potential , membrane permeability , membrane , patch clamp , biochemistry , biology , condensed matter physics , stereochemistry , physics , receptor , organic chemistry , nuclear magnetic resonance spectroscopy
1. When one hyperpolarizes a muscle fibre by passing electric current, the K conductance declines with time. Voltage‐clamp experiments on frog sartorius muscle fibres showed that two components contribute to this decline. 2. A rapid component operates when the fibre is hyperpolarized to potentials more negative than −120 mV. Decline by this mechanism is reversed completely within 200 msec. The large effect of temperature on the kinetics of this process indicates that it represents a time‐dependent membrane permeability change. 3. A slow component operates also at less negative potentials. Recovery at −65 mV takes place with half‐times of about 0·4 sec. The Q 10 for the rate of recovery is 1·3, indicating that this process is diffusion limited. 4. After prolonged hyperpolarization to potentials positive to −120 mV, membrane current at the resting potential is outward and persists for several seconds. At that time, the potential measured in the absence of membrane current is shifted in the negative direction by 3–5 mV. 5. This shift and the time course of currents near the resting potential after hyperpolarization as well as the Q 10 of 1·3 indicate that the slow process is due to changes in tubular K concentration and not to a time‐dependent membrane permeability change. 6. At potentials less negative than −120 mV, tubular depletion can satisfactorily account for the decline of K conductance. At more negative potentials, the decline appears to be due to both depletion and a permeability change.