The effect of the CO2/HCO 3 − buffer system on the membrane potential of frog skeletal muscle

1977 ◽  
Vol 371 (3) ◽  
pp. 179-184
Author(s):  
Walter Reber ◽  
François Huguenin
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Buffer System ◽  
Frog Skeletal Muscle

scholarly journals Strophanthidin-sensitive sodium fluxes in metabolically poisoned frog skeletal muscle.

1976 ◽  
Vol 68 (4) ◽  
pp. 405-420 ◽  
Author(s):  
B G Kennedy ◽  
P De Weer
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Human Erythrocyte ◽  
Sodium Pump ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Frog Skeletal Muscle ◽  
Na Efflux ◽  
Unidirectional Fluxes ◽  
External K

Strophanthidin-sensitive and insensitive unidirectional fluxes of Na were measured in fog sartorius muscles whose internal Na levels were elevated by overnight storage in the cold. ATP levels were lowered, and ADP levels raised, by metabolic poisoning with either 2,4-dinitrofluorobenzene or iodoacetamide. Strophanthidin-sensitive Na efflux and influx both increased after poisoning, while strophanthidin-insensitives fluxes did not. The increase in efflux did not require the presence of external K but was greatly attenuated when Li replaced Na as the major external cation. Membrane potential was not markedly altered by 2,4-dinitrofluorobenzene. These observations indicate that the sodium pump of frog skeletal muscle resembles that of squid giant axon and human erythrocyte in its ability to catalyze Na-Na exchange to an extent determined by intracellular ATP/ADP levels.

Mechanism of insulin action on resting membrane potential of frog skeletal muscle

1979 ◽  
Vol 236 (5) ◽  
pp. C249-C254 ◽  
Author(s):  
R. D. Moore ◽  
J. L. Rabovsky
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Insulin Action ◽  
External Surface ◽  
Resting Membrane Potential ◽  
Frog Skeletal Muscle ◽  
Na Pump ◽  
Frog Sartorius ◽  
K Permeability ◽  
Stimulation Of

At a concentration that stimulates the Na pump, insulin hyperpolarizes the plasma membrane of frog sartorius in the presence of substrate-free Ringer. The hyperpolarization ranged from 3.5 to 7.3 mV and averaged 4.7 mV. Ouabain, 10(-4) M, completely blocked the effect of insulin on the membrane potential. Moreover, ouabain completely reversed the insulin-induced hyperpolarization within 20 min. The hyperpolarization produced by insulin was not associated with a detectable increase in the ratio of K+ permeability to Na+ permeability nor with a detectable increase in the concentration of intracellular K+, although a depletion of K+ near the external surface of the membrane cannot be excluded. The results clearly indicate that the hyperpolarization is secondary to stimulation of the Na pump by insulin.

Unidirectional flux ratio for potassium ions in depolarized frog skeletal muscle

1981 ◽  
Vol 241 (1) ◽  
pp. C68-C75 ◽  
Author(s):  
B. C. Spalding ◽  
O. Senyk ◽  
J. G. Swift ◽  
P. Horowicz
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Flux Ratio ◽  
External Solution ◽  
Resting Potential ◽  
Frog Skeletal Muscle ◽  
High K ◽  
Sigmoidal Curve ◽  
K Concentration ◽  
Low K

Small bundles of frog skeletal muscle fibers were loaded with 305 mM K+ and 120 mM Cl-, and 42K+ tracer efflux and influx were measured as a function of external K+ concentration ([K+]o) at a resting potential of -2 mV. As [K+]o was lowered from 305 mM, efflux decreased along a markedly sigmoidal curve, reaching a constant nonzero value at low [K+]o. Influx varied linearly with [K+]o at low [K+]o and more steeply at higher [K+]o. The ratio of influx to efflux was described by the equation: influx/efflux = exp[-n(V - VK)F/RT] with n = 2 at high [K+]o, but the ratio approached this equation with n = 1 at low [K+]o. Efflux did not depend on [K+]o when the membrane potential was raised to +36 mV, whereas at low [K+]o decreasing the membrane potential to -19 mV further activated the efflux. The results are discussed in terms of an inwardly rectifying potassium channel with two or more activating sites within the membrane that bind K+ and are accessible from the external solution.

scholarly journals Kinetic and pharmacological properties of the sodium channel of frog skeletal muscle.

1976 ◽  
Vol 67 (3) ◽  
pp. 309-323 ◽  
Author(s):  
D T Campbell ◽  
B Hille
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Dissociation Constants ◽  
Quantitative Description ◽  
Potential Drop ◽  
Na Channels ◽  
Frog Skeletal Muscle ◽  
Myelinated Nerve ◽  
Sodium Permeability ◽  
Block Of Na Channels

Na channels of frog skeletal muscle are studied under voltage clamp and their properties compared with those of frog myelinated nerve. A standard mathematical model is fitted to the sodium currents measured in nerve and in muscle to obtain a quantitative description of the gating kinetics. At 5 degrees C the kinetics in frog nerve and skeletal muscle are similar except that activation proceeds five times faster in nerve. Block of Na channels by saxitoxin is measured in nerve and in muscle. The apparent dissociation constants for the inhibitory complex are about 1 nM and not significantly different in nerve and muscle. Block of Na channels by external protons in muscle is found to have an apparent pKalpha of 5.33 and a voltage dependence corresponding to action of 27% of the membrane potential drop. Both values are like those for nerve. Shift of the peak sodium permeability-membrane potential curve with changes of external pH and Ca++ are found to be the same in nerve and muscle. It is concluded that Na channels of nerve and muscle are nearly the same.

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