scholarly journals The Control of the Membrane Potential of Muscle Fibers by the Sodium Pump

1965 ◽  
Vol 48 (5) ◽  
pp. 761-775 ◽  
Author(s):  
L. J. Mullins ◽  
M. Z. Awad
Keyword(s):  
Membrane Potential ◽  
Extracellular Space ◽  
Sodium Pump ◽  
Muscle Fibers ◽  
Electrical Potential ◽  
Lithium Sulfate ◽  
Ringer’S Solution ◽  
Na Efflux ◽  
Frog Sartorius ◽  
Considerable Range

Frog sartorius muscles were made Na-rich by immersion in K-free sulfate Ringer's solution in the cold. The muscles were then loaded with Na24 and the extracellular space cleared of radioactivity. When such Na-rich muscles were transferred to lithium sulfate Ringer's solution at 20°C, Na efflux was observed to increase with time, to reach a maximum about 15 minutes after the transfer of the muscles to Li2SO4, and then to decline. The decline in efflux from these muscles was proportional to ([Na]i)8 over a considerable range of [Na]i. The membrane potential of Na-rich muscles was about -48 mv in K-free sulfate Ringer's at 4°C but changed to -76 mv in the same solution at 20°C and to -98 mv in Li2SO4 Ringer's at 20°C. By contrast, muscles with a normal [Na]i showed a fall in membrane potential when transferred from K-free sulfate Ringer's to Li2SO4 Ringer's solution. The general conclusions from this study are (a) that Na extrusion is capable of generating an electrical potential, and (b) that increases in [Na]i lead to reversible increases in PNa of muscle fibers.

scholarly journals The Influence of Sodium-Free Solutions on the Membrane Potential of Frog Muscle Fibers

1963 ◽  
Vol 47 (1) ◽  
pp. 117-132 ◽  
Author(s):  
L. J. Mullins ◽  
K. Noda
Keyword(s):  
Membrane Potential ◽  
Activity Coefficients ◽  
Muscle Fibers ◽  
Frog Muscle ◽  
Sartorius Muscle ◽  
Coupling Ratio ◽  
Nernst Equation ◽  
Ringer’S Solution ◽  
Na Efflux ◽  
Frog Sartorius

The membrane potential of frog sartorius muscle fibers in a Cl- and Na-free Ringer's solution when sucrose replaces NaCl is about the same as that in normal Ringer's solution. The K+ efflux is also about the same in the two solutions but muscles lose K and PO4 in sucrose Ringer's solutions. The membrane potential in sucrose Ringer's solution is equal to that given by the Nernst equation for a K+ electrode, when corrections are made for the activity coefficients for K+ inside and outside the fiber. For a muscle in normal Ringer's solution, the measured membrane potential is within a few millivolts of EK. This finding is incompatible with a 1:1 coupled Na-K pump. It is consistent with either no coupling of Na efflux to K influx, or a coupling ratio of 3 or greater.

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.

Action of acetylcholine, choline and D-tubocurarine on the membrane of frog sartorius muscle fibers

1959 ◽  
Vol 196 (6) ◽  
pp. 1191-1196 ◽  
Author(s):  
S. Ochs ◽  
A. K. Mukherjee
Keyword(s):  
Membrane Potential ◽  
Mechanical Stimulation ◽  
Muscle Fibers ◽  
Potential Drop ◽  
Sartorius Muscle ◽  
End Plate ◽  
Frog Sartorius Muscle ◽  
Before And After ◽  
The Mean ◽  
Frog Sartorius

Resting potentials of frog sartorius muscle fibers were taken with microelectrodes at different distances along the length of muscles before and after adding acetylcholine or choline. The mean membrane potential drop and scatter of the potentials recorded in the relatively nerve-free, and in the more densely innervated parts of the muscle, were similar. The loss of direct excitability to electrical and mechanical stimulation was correlated with the concentration of choline or acetylcholine presented. d-tubocurarine added beforehand protected against the depolarizing effect of acetylcholine and choline everywhere along the length of the muscle. A generalized action of acetylcholine and choline and also of d-tubocurarine all along the muscle fibers was inferred. This generalized action at higher concentrations of acetylcholine and choline is believed to be additional to a more specific end plate action.

scholarly journals The Effect of Caffeine on Radiocalcium Movement in Frog Sartorius

1961 ◽  
Vol 44 (5) ◽  
pp. 845-858 ◽  
Author(s):  
C. P. Bianchi
Keyword(s):  
Calcium Influx ◽  
Muscle Fibers ◽  
Thermodynamic Activity ◽  
Potassium Depolarization ◽  
Ionic Activity ◽  
Contractile State ◽  
Ringer’S Solution ◽  
Frog Sartorius

Caffeine increases resting calcium influx approximately threefold in normally polarized and in potassium-depolarized fibers of frog sartorius muscles. It does not affect the transient rapid increase in calcium influx that occurs at the beginning of a potassium depolarization. Calcium outflux in Ringer's solution, in zero calcium Ringer's solution, and in zero calcium Ringer's solution plus 0.004 M EDTA is also markedly increased by caffeine. The increased outflux reaches a rate which is approximately the same as the increased calcium influx. One interpretation of the findings is that caffeine reduces the binding of calcium both in the membrane and in the myoplasm; this increases the "permeability" to calcium and the ionic activity of calcium in muscle. This interpretation is consistent with the view that the contractile state of muscle is dependent at least in part on the thermodynamic activity of calcium in the muscle fibers.

scholarly journals SELECTIVE DISRUPTION OF THE SARCOTUBULAR SYSTEM IN FROG SARTORIUS MUSCLE

1968 ◽  
Vol 39 (2) ◽  
pp. 451-467 ◽  
Author(s):  
Brenda Eisenberg ◽  
Robert S. Eisenberg
Keyword(s):  
Extracellular Space ◽  
Skeletal Muscles ◽  
Muscle Fibers ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Normal Muscle ◽  
Tubular System ◽  
Sarcotubular System ◽  
Reliable Marker ◽  
Frog Sartorius

Skeletal muscles which have been soaked for 1 hr in a glycerol-Ringer solution and then returned to normal Ringer solution have a disrupted sarcotubular system. The effect is associated with the return to Ringer's since muscles have normal fine structure while still in glycerol-Ringer's. Karnovsky's peroxidase method was found to be a very reliable marker of extracellular space, filling 98.5% of the tubules in normal muscle. It was interesting to note that only 84.1% of the sarcomeres in normal muscle have transverse tubules. The sarcotubular system was essentially absent from glycerol-treated muscle fibers, only 2 % of the tubular system remaining connected to the extracellular space; the intact remnants were stumps extending only a few micra into the fiber. Thus, glycerol-treated muscle fibers provide a preparation of skeletal muscle with little sarcotubular system. Since the sarcoplasmic reticulum is not destroyed and the sarcolemma and myofilaments are intact in this preparation, of the properties of the sarcolemma may thus be separated from those of the tubular system.

Changes in membrane potentials, K content, and fiber structure in irradiated frog sartorius muscle

1960 ◽  
Vol 198 (4) ◽  
pp. 709-714 ◽  
Author(s):  
Edgar B. Darden
Keyword(s):  
Membrane Potential ◽  
Membrane Potentials ◽  
Sartorius Muscle ◽  
Fiber Structure ◽  
Ringer’S Solution ◽  
Intact Muscle ◽  
Radiation Induced ◽  
Induced Changes ◽  
Histologic Changes ◽  
Frog Sartorius

Changes in membrane potential, K content, and fiber structure were studied in excised frog sartorius muscles that had received massive single doses (50–200 kr) of ionizing radiation. With muscle in normal Ringer's solution at 25°C, the median membrane potential declined and K leakage increased progressively, as measured at intervals, after exposure doses above ∼100 kr; in K-rich Ringer's solution, decline was appreciably slower. In individual irradiated fibers, membrane potentials recorded at different points along a fiber tended to be nonuniform. When subsequent histologic alteration occurred, it often originated as a focal disorganization of structure in a region of minimum membrane potential. Visible pathologic changes resembled in part Zenker degeneration in intact muscle. It is suggested that decline in membrane potential, histologic changes, and increased K leakage are different expressions of the same basic radiation lesion. Radiation-induced changes were markedly retarded by posttreatment storage at 3°C.

scholarly journals Effect of membrane polarization on contractile threshold and time course of prolonged contractile responses in skeletal muscle fibers.

1984 ◽  
Vol 84 (6) ◽  
pp. 927-943 ◽  
Author(s):  
C Caputo ◽  
P Bolaños ◽  
G F Gonzalez
Keyword(s):  
Membrane Potential ◽  
Time Course ◽  
Muscle Fibers ◽  
Fiber Membrane ◽  
Activation Curve ◽  
Contractile Responses ◽  
Membrane Polarization ◽  
Peak Tension ◽  
Relaxation Phase ◽  
Ringer’S Solution

Short muscle fibers (less than 1.5 mm) from the m. lumbricalis IV digiti of Rana pipiens were voltage-clamped at -100 mV with a two-microelectrode technique, in normal Ringer's solution containing 10(-6) g/ml tetrodotoxin. The activation curve relating peak tension to membrane potential could be shifted toward more negative or less negative potential values by hyperpolarizing or depolarizing the fiber membrane to -130, -120, or -70 mV, respectively, which indicates that contractile threshold depends on the fiber membrane potential. Long (greater than 5 s) depolarizing (90 mV) pulses induce prolonged contractile responses showing a plateau and a rapid relaxation phase similar to K contractures. Conditioning hyperpolarizations prolong the time course of these responses, while conditioning depolarizations shorten it. The shortening of the response time course, which results in a decrease of the area under the response, is dependent on the amplitude and duration of the conditioning depolarization. Depending on the magnitude and duration, a conditioning depolarization may also reduce peak tension. When the area under the response is reduced by 50%, the level of membrane potential also affects the repriming rate. During repriming, peak tension is restored before the contracture area. Thus, when peak tension is reprimed to 80%, the area is reprimed by 50% of its normal value. Repriming has a marked temperature dependency with a Q10 higher than 4. These results are compatible with the idea that an inactivation process, voltage and time dependent, regulates the release of calcium from the sarcoplasmic reticulum during these responses.

scholarly journals Sodium and potassium fluxes and membrane potential of human neutrophils: evidence for an electrogenic sodium pump.

1982 ◽  
Vol 79 (3) ◽  
pp. 453-479 ◽  
Author(s):  
L Simchowitz ◽  
I Spilberg ◽  
P De Weer
Keyword(s):  
Membrane Potential ◽  
Sodium Pump ◽  
Membrane Conductance ◽  
Human Neutrophils ◽  
Constant Field ◽  
Electrogenic Sodium Pump ◽  
Na Efflux ◽  
The Individual ◽  
Sodium And Potassium ◽  
External K

Sodium and potassium ion contents and fluxes of isolated resting human peripheral polymorphonuclear leukocytes were measured. In cells kept at 37 degrees C, [Na]i was 25 mM and [K]i was 120 mM; both ions were completely exchangeable with extracellular isotopes. One-way Na and K fluxes, measured with 22Na and 42K, were all approximately 0.9 meq/liter cell water . min. Ouabain had no effect on Na influx or K efflux, but inhibited 95 +/- 7% of Na efflux and 63% of K influx. Cells kept at 0 degree C gained sodium in exchange for potassium ([Na]i nearly tripled in 3 h); upon rewarming, ouabain-sensitive K influx into such cells was strongly enhanced. External K stimulated Na efflux (Km approximately 1.5 mM in 140-mM Na medium). The PNa/PK permeability ratio, estimated from ouabain insensitive fluxes, was 0.10. Valinomycin (1 microM) approximately doubled PK. Membrane potential (Vm) was estimated using the potentiometric indicator diS-C3(5); calibration was based on the assumption of constant-field behavior. External K, but not Cl, affected Vm. Ouabain caused a depolarization whose magnitude dependent on [Na]i. Sodium-depleted cells became hyperpolarized when exposed to the neutral exchange carrier monensin; this hyperpolarization was abolished by ouabain. We conclude that the sodium pump of human peripheral neutrophils is electrogenic, and that the size of the pump-induced hyperpolarization is consistent with the membrane conductance (3.7-4.0 microseconds/cm2) computed from the individual K and Na conductances.

Prepotentials and unidirectional propagation in myocardium

1961 ◽  
Vol 201 (5) ◽  
pp. 873-880 ◽  
Author(s):  
T. Hoshiko ◽  
Nick Sperelakis
Keyword(s):  
Current Flow ◽  
Reverse Direction ◽  
Sartorius Muscle ◽  
Potential Response ◽  
Ringer’S Solution ◽  
Current Pulses ◽  
Negative Current ◽  
Reversed Polarity ◽  
Bidirectional Propagation ◽  
Frog Sartorius

In frog ventricular strips bathed in Ca-free Ringer's solution containing 6–30 mm/liter Mg and treated with conditioning current pulses, propagation became impaired. An exaggerated foot, or prepotential, was consistently more prominent when the conditioned strip was stimulated from one end than from the other. Occasionally a prepotential in isolation alternated with a prepotential plus action potential response. After further treatment with current pulses, propagation failed in the direction of negative current flow. Thresholds of impaled cells were identical. Bidirectional propagation was restored in Ringer's solution. Conditioning pulses of reversed polarity induced unidirectional propagation in the reverse direction. Propagation in frog sartorius muscle was not blocked under similar conditions. Prepotentials and unidirectional propagation may be explained by junctional transmission from cell to cell.

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