Effects of external K concentration on the electrogenicity of the insulin-stimulated Na,K-pump in frog skeletal muscle

1986 ◽  
Vol 91 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Yoshinori Marunaka
Keyword(s):  
Skeletal Muscle ◽  
Frog Skeletal Muscle ◽  
K Concentration ◽  
External K

K+-stimulated sugar uptake in skeletal muscle: role of cytoplasmic Ca2+

1983 ◽  
Vol 245 (1) ◽  
pp. C125-C132 ◽  
Author(s):  
P. Valant ◽  
D. Erlij
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cytochalasin B ◽  
Sugar Transport ◽  
Sugar Uptake ◽  
Frog Skeletal Muscle ◽  
High K ◽  
K Concentration ◽  
External K

We have compared the effects of insulin with those of elevated external K+ concentration ([K+]o) on sugar uptake and protein synthesis by frog skeletal muscle. When [K+]o was between 0.5 and 15 mM there were no effects on uptake; however, when 20 mM was used a significant increase was observed. Further increases in [K+]o caused larger stimulations of uptake. The stimulation persisted for 2.5 h after washing the high [K+]o. The stimulations caused by both insulin and high K+ were markedly inhibited by cytochalasin B. Dantrolene nearly abolished the response to high K+, whereas it had only minor effects on the resting sugar uptake and on the stimulations caused by either insulin or epinephrine. These results suggest that while both insulin and high K+ activate the cytochalasin-sensitive transport system of sugar transport, each agent must act through a different pathway, because only the effects of high K+ were dantrolene sensitive. The effect of dantrolene suggests that the enhancement of sugar transport caused by high K+ is due to an increase of cytoplasmic Ca2+. In contrast to insulin, high K+ did not modify the rate of protein synthesis.

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.

Enhancement (by ATP, insulin, and lack of divalent cations) of ouabain inhibition of cation transport and ouabain binding in frog skeletal muscle; effect of insulin and ouabain on sarcolemmal (Na + K)MgATPase

1977 ◽  
Vol 55 (1) ◽  
pp. 21-33 ◽  
Author(s):  
J. F. Manery ◽  
E. E. Dryden ◽  
J. S. Still ◽  
G. Madapallimattam
Keyword(s):  
Skeletal Muscle ◽  
Extracellular Space ◽  
Divalent Cations ◽  
Membrane Surface ◽  
Cation Transport ◽  
Frog Skeletal Muscle ◽  
Ouabain Binding ◽  
Maximum Inhibition ◽  
Ouabain Inhibition ◽  
External K

Using small, intact frog muscles, the basic properties of Na+ and K+ transport were shown to resemble those of the (Na+ + K+) Mg2+ATPase (EC 3.6.1.3) isolated from skeletal muscle, (a) External K+ is essential for Na+ exit and K+ entry after the muscles are Na+-loaded and K+-depleted; (b) the ouabain concentration causing maximum inhibition of recovery is the same for transport as for the inhibition of the isolated enzyme. Ouabain causes a decrease in the sorbitol space and causes muscle fibre swelling. Absence of Ca2+ and Mg2+ inhibits recovery of normal Na+ and K+ concentrations and increases the sorbitol space. Insulin stimulates K+ uptake and Na+ loss in intact muscles but has no effect on the isolated sarcolemmal (Na+ + K+) Mg2+ATPase. Absence of divalent cations, addition of external ATP and of insulin enhance the ouabain inhibition of recovery.Bound ouabain was measured using [3H]ouabain and [14C]sorbitol (to measure the extracellular space). The process of binding was slowly reversible and was saturable within a range of ouabain concentrations from 1.48 × 10−7 to 5.96 × 10−7 M. From the nonexchangeable ouabain bound, the density of glycoside receptors was estimated to be 650 molecules per square micrometre of membrane surface. The absence of divalent cations, addition of external ATP and of insulin significantly enhanced the amount of ouabain bound. Substitution of Na+ and K+ by choline greatly reduced the bound ouabain.

Excitation—contraction coupling in skeletal and caudal heart muscle of the hagfishEptatretus burgeriGirard

2002 ◽  
Vol 205 (22) ◽  
pp. 3535-3541
Author(s):  
Isao Inoue ◽  
Izuo Tsutsui ◽  
Quentin Bone
Keyword(s):  
Skeletal Muscle ◽  
Heart Muscle ◽  
Force Generation ◽  
Muscle Fibres ◽  
Fast Skeletal Muscle ◽  
K Concentration ◽  
Electrical Stimuli ◽  
Skeletal Muscle Fibres ◽  
Coupling Mechanisms ◽  
External K

SUMMARYHagfishes are regarded as the most primitive living craniates. Excitation—contraction (E—C) coupling mechanisms were studied in skeletal and caudal heart muscle fibres of the hagfish Eptatretus burgeri. In white (fast) skeletal muscle fibres from the musculus tubulatus, force generation in response to electrical stimulation was maintained in nominally Ca2+ free artificial seawater (ASW)(0Ca2+-ASW) containing 10 mmol l-1 Co2+ (a blocker of Ca2+ currents). Similarly, in red (slow) fibres from parietal muscle bathed in 0Ca2+-ASW containing 10 mmol l-1 Co2+, force generation occurred in association with K+ depolarisation when the external K+ concentration was increased to 100 mmol l-1. Therefore, external Ca2+ is not required for muscle contraction. Hence, both white and red fibres possess the function of depolarisation-induced Ca2+-release from intracellular Ca2+ stores. This function is the same as in the skeletal muscle of all other vertebrates. In caudal heart muscle fibres,twitches in response to electrical stimuli were maintained in 0Ca2+-ASW containing 30 mmol l-1 Co2+. In fibres loaded with fluo-3 bathed in 0Ca2+-ASW containing 30 mmol l-1 Co2+, an increase in the intracellular free Ca2+ level associated with K+ depolarisation was observed after the external K+ concentration was increased to 100 mmol l-1. Thus E—C coupling in the caudal heart muscle is also of the vertebrate skeletal muscle type.

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.

Ultra-Rapid Freezing of Isolated Skeletal Muscle Fibers

1977 ◽  
Vol 35 ◽  
pp. 576-577
Author(s):  
Joachim R. Sommer ◽  
Nancy R. Wallace
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Granular Material ◽  
Nuclear Envelope ◽  
Intracellular Calcium ◽  
Ruthenium Red ◽  
Threshold Concentration ◽  
Rapid Freezing ◽  
Frog Skeletal Muscle ◽  
Electrical Isolation

After Howell (1) had shown that ruthenium red treatment of fixed frog skeletal muscle caused collapse of the intermediate cisternae of the sarcoplasmic reticulum (SR), forming a pentalaminate structure by obi iterating the SR lumen, we demonstrated that the phenomenon involves the entire SR including the nuclear envelope and that it also occurs after treatment with other cations, including calcium (2,3,4).From these observations we have formulated a hypothesis which states that intracellular calcium taken up by the SR at the end of contraction causes the M rete to collapse at a certain threshold concentration as the first step in a subsequent centrifugal zippering of the free SR toward the junctional SR (JSR). This would cause a) bulk transport of SR contents, such as calcium and granular material (4) into the JSR and, b) electrical isolation of the free SR from the JSR.

Electron Probe Analysis of Muscle

1982 ◽  
Vol 40 ◽  
pp. 398-401
Author(s):  
A. V. Somlyo ◽  
H. Shuman ◽  
A. P. Somlyo
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Resting State ◽  
Binding Sites ◽  
Electron Probe ◽  
Frog Skeletal Muscle ◽  
Electron Probe Analysis ◽  
Probe Analysis

Electron probe analysis of frozen dried cryosections of frog skeletal muscle, rabbit vascular smooth muscle and of isolated, hyperpermeab1 e rabbit cardiac myocytes has been used to determine the composition of the cytoplasm and organelles in the resting state as well as during contraction. The concentration of elements within the organelles reflects the permeabilities of the organelle membranes to the cytoplasmic ions as well as binding sites. The measurements of [Ca] in the sarcoplasmic reticulum (SR) and mitochondria at rest and during contraction, have direct bearing on their role as release and/or storage sites for Ca in situ.

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