scholarly journals Contributions of the sodium pump and ionic gradients to the membrane potential of a molluscan neurone

1970 ◽  
Vol 210 (4) ◽  
pp. 897-917 ◽  
Author(s):  
A. L. F. Gorman ◽  
M. F. Marmor
Keyword(s):  
Membrane Potential ◽  
Sodium Pump ◽  
Molluscan Neurone

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.

The diffusion and electrogenic components of the membrane potential of hypoxic myocardium

1987 ◽  
Vol 65 (2) ◽  
pp. 246-251 ◽  
Author(s):  
Normand Leblanc ◽  
Elena Ruiz-Ceretti
Keyword(s):  
Membrane Potential ◽  
Sodium Pump ◽  
Resting Potential ◽  
Krebs Solution ◽  
Ventricular Muscle ◽  
Diffusion Component ◽  
K Concentration ◽  
Zero Potential ◽  
K Permeability ◽  
External K

The diffusion and electrogenic components of the resting potential of hypoxic ventricular muscle were separated by inhibition of the sodium pump with 10−4 M ouabain. The response to varying external K concentrations (Ko) was studied. Arteriaily perfused rabbit hearts were submitted to 60 min hypoxia in Krebs solution containing 5 mM K throughout or to different external K concentrations during the last 20 min of hypoxia. For K concentrations between 1.5 and 10 mM, hypoxia did not change the resting potential except for a slight hyperpolarization in 7.5 mM K. The diffusion component of the resting potential did not differ from the resting potential at Ko < 5 mM. An electrogenic potential of −3 to −6 mV was detectable at Ko values between 5 and 10 mM. The internal K concentration, Ki, was estimated from extrapolations to zero potential of the relation resting potential vs. Ko in normoxic and hypoxic hearts. These experiments revealed a decline of Ki of 16 mM with hypoxia. The variation of the diffusion potential with external K was fitted by a PNa:PK ratio five times lower than in normoxia. It has been concluded that an increase in K permeability and the persistence of electrogenic Na extrusion during hypoxia of rather short duration prevent membrane depolarization despite the myocardial K loss.

Electrogenic sodium-dependent glycine transport in sheep reticulocytes

1978 ◽  
Vol 56 (6) ◽  
pp. 545-551 ◽  
Author(s):  
Stephen Benderoff ◽  
Rose M. Johnstone ◽  
Rhoda Blostein
Keyword(s):  
Membrane Potential ◽  
Sodium Pump ◽  
Marked Decrease ◽  
Massive Bleeding ◽  
Atp Content ◽  
Chemical Gradient ◽  
Electrogenic Sodium Pump ◽  
Sodium Dependent ◽  
Glycine Transport ◽  
Measurable Change

Na+-dependent glycine transport has been studied in reticulocyte-enriched fractions of blood obtained after massive bleeding of sheep. The activity is dependent on the sodium electrochemical potential and the membrane potential. The sodium chemical gradient was varied by changing either external or internal Na+ and the membrane potential, by addition of valinomycin. Similar results were obtained with resealed reticulocyte ghosts. Under conditions optimal for sodium pumping (intracellular Na+ > 50 mM), ouabain inhibited glycine uptake prior to any measurable change in the cellular Na+ suggesting that in these cells an electrogenic sodium pump is sufficiently active to contribute to the membrane potential. Na+-dependent glycine transport undergoes a marked decrease during Song-term incubation at 37 °C. During this time, the cells maintain their integrity and ATP content but undergo maturation as evidenced in the decrease in cells with reticulocyte morphology.

scholarly journals Stimulation of Sodium Pump Restores Membrane Potential to Neurons Excited by Glutamate in Zebrafish Distal Retina

2003 ◽  
Vol 549 (3) ◽  
pp. 787-800 ◽  
Author(s):  
Ralph Nelson ◽  
Anna M. Bender ◽  
Victoria P. Connaughton
Keyword(s):  
Membrane Potential ◽  
Sodium Pump ◽  
Stimulation Of

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.

Rhythmic coronary arterial contractions: changes with time and membrane potential

1986 ◽  
Vol 250 (3) ◽  
pp. H524-H529 ◽  
Author(s):  
K. D. Keef ◽  
G. Ross
Keyword(s):  
Membrane Potential ◽  
Coronary Artery ◽  
Time Course ◽  
Sodium Pump ◽  
Contractile Response ◽  
Resting Membrane Potential ◽  
Krebs Solution ◽  
Contractile Responses ◽  
Rabbit Coronary Artery ◽  
Rhythmic Contractions

Responses of isolated rabbit coronary artery segments to KCl and 2-(2-aminoethyl)-pyridine (AEP) were studied. Vessels stored at 2 degrees C for 24 h developed spontaneous rhythmic contractions during the first 20 min in Krebs solution at 37 degrees C. The contractile response to KCl or AEP declined to a minimum at 60 min [i.e., time zero (to) +60], increased to a peak at to +150 and then again declined. Resting membrane potential (Em) was less than or equal to -40 mV at to +20, -70 mV at to +30-60 and -50 mV at to +240-360 min. Rhythmic contractile responses were frequent and were associated with changes in Em. Vessels that were not cold stored did not hyperpolarize, nor did they show the early decline in response. Vessels stored at 2 degrees C for 24 h and then tested at 22-23 degrees C exhibited a similar pattern of changes in contraction but the time course was more protracted. We conclude that contractile responses are initially modulated by changes in Em associated with an increase then decrease in the activity of the sodium pump. Later changes in reactivity are due to a different mechanism.

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