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.

Ca(2+)- and pH-dependent halothane stimulation of Ca2+ release in sarcoplasmic reticulum from frog muscle

1996 ◽  
Vol 271 (2) ◽  
pp. C540-C546 ◽  
Author(s):  
M. Beltran ◽  
R. Bull ◽  
P. Donoso ◽  
C. Hidalgo
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Release Kinetics ◽  
Frog Muscle ◽  
Time Range ◽  
Frog Skeletal Muscle ◽  
Open Probability ◽  
Filtration System ◽  
Stimulation Of

The effect of halothane on calcium release kinetics was studied in triad-enriched sarcoplasmic reticulum vesicles from frog skeletal muscle. Release from vesicles passively equilibrated with 3 mM 45CaCl2 was measured in the millisecond time range by use of a fast-filtration system. Halothane (400 microM) increased release rate constants at pH 7.1 and 7.4 as a function of extravesicular pCa. In contrast, halothane at pH 6.8 produced the same stimulation of release from pCa 7.0 to 3.0; no release took place in these conditions in the absence of halothane. Halothane shifted the calcium activation curve at pH 7.1, but not at pH 7.4, to the left and increased channel open probability at pH 7.1 in the cis pCa range of 7.0 to 5.0. These results indicate that cytosolic pCa and pH modulate the stimulatory effects of halothane on calcium release. Furthermore, halothane stimulated release in frog skeletal muscle at low pH and resting calcium concentration, indicating that in frog muscle halothane can override the closing of the release channels produced by these conditions, as it does in malignant hyperthermia-susceptible porcine 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.

Effect of disuse on the resting membrane potential of skeletal muscle

1979 ◽  
Vol 64 (1) ◽  
pp. 231-234 ◽  
Author(s):  
Elis F. Stanley ◽  
Daniel B. Drachman
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Resting Membrane Potential

Development of membrane conductance of chick skeletal muscle in culture

1980 ◽  
Vol 58 (6) ◽  
pp. 600-605 ◽  
Author(s):  
C. M. Thomson ◽  
W. F. Dryden
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Initial Level ◽  
Potassium Conductance ◽  
Membrane Conductance ◽  
Resting Membrane Potential ◽  
Membrane Conductances ◽  
Rapid Changes ◽  
Fibre Development

Resting membrane potentials and membrane conductances of chick skeletal muscle in culture were determined from the 3rd to the 10th day after plating. The effect of tetraethylammonium (TEA) and of replacement of potassium with caesium on these parameters was investigated. Resting membrane potential (Em) rises during myogenesis in vitro and resting membrane conductance (Gm) falls. The initial level of Gm was relatively high (1.2 mS cm−2) but this fell to a final level around 0.2 mS cm−2. The most rapid changes in both parameters occurred between days 3 and 5 of culture. Both TEA and caesium depressed Em and Gm at all stages of development. On the 3rd day of culture Gm was reduced by 0.2 mS cm−2 by both agents. Thereafter, Gm was depressed by about 0.1 mS cm−2. Caesium does not penetrate potassium channels and the reduction in Gm is attributed to block of these channels. This indicates that resting potassium conductance is relatively constant at 0.1 mS cm−2 throughout muscle fibre development. Because TEA produces changes in Gm similar to those produced by caesium, TEA is concluded to be acting at the potassium channel in a manner similar to caesium.

scholarly journals Human Myoblast Fusion Requires Expression of Functional Inward Rectifier Kir2.1 Channels

2001 ◽  
Vol 153 (4) ◽  
pp. 677-686 ◽  
Author(s):  
Jacqueline Fischer-Lougheed ◽  
Jian-Hui Liu ◽  
Estelle Espinos ◽  
David Mordasini ◽  
Charles R. Bader ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Muscle Development ◽  
Myoblast Fusion ◽  
Inward Rectifier ◽  
Resting Membrane Potential ◽  
Skeletal Muscle Development ◽  
K Channels ◽  
Window Current ◽  
Human Myoblast

Myoblast fusion is essential to skeletal muscle development and repair. We have demonstrated previously that human myoblasts hyperpolarize, before fusion, through the sequential expression of two K+ channels: an ether-à-go-go and an inward rectifier. This hyperpolarization is a prerequisite for fusion, as it sets the resting membrane potential in a range at which Ca2+ can enter myoblasts and thereby trigger fusion via a window current through α1H T channels.

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