scholarly journals The Ionic Basis of Electrical Activity in Embryonic Cardiac Muscle

1968 ◽  
Vol 52 (4) ◽  
pp. 666-681 ◽  
Author(s):  
Billy K. Yeh ◽  
Brian F. Hoffman
Keyword(s):  
Electrical Activity ◽  
Sodium Concentration ◽  
Cardiac Cells ◽  
Resting Potential ◽  
Extracellular Potassium ◽  
Embryonic Chick ◽  
Extracellular Potassium Concentration ◽  
Chick Heart ◽  
Extracellular Sodium ◽  
Ionic Basis

The intracellular sodium concentration reported for young, embryonic chick hearts is extremely high and decreases progressively throughout the embryonic period, reaching a value of 43 mM immediately before hatching. This observation suggested that the ionic basis for excitation in embryonic chick heart may differ from that responsible for electrical activity of the adult organ. This hypothesis was tested by recording transmembrane resting and action potentials on hearts isolated from 6-day and 19-day chick embryos and varying the extracellular sodium and potassium concentrations. The results show that for both young and old embryonic cardiac cells the resting potential depends primarily on the extracellular potassium concentration and the amplitude and rate of rise of the action potential depend primarily on the extracellular sodium concentration.

scholarly journals The Ionic Basis of Electrical Activity in Embryonic Cardiac Muscle

1968 ◽  
Vol 52 (3) ◽  
pp. 666-681 ◽  
Author(s):  
Billy K. Yeh ◽  
Brian F. Hoffman
Keyword(s):  
Electrical Activity ◽  
Sodium Concentration ◽  
Cardiac Cells ◽  
Resting Potential ◽  
Extracellular Potassium ◽  
Embryonic Chick ◽  
Extracellular Potassium Concentration ◽  
Chick Heart ◽  
Extracellular Sodium ◽  
Ionic Basis

The intracellular sodium concentration reported for young, embryonic chick hearts is extremely high and decreases progressively throughout the embryonic period, reaching a value of 43 mM immediately before hatching. This observation suggested that the ionic basis for excitation in embryonic chick heart may differ from that responsible for electrical activity of the adult organ. This hypothesis was tested by recording transmembrane resting and action potentials on hearts isolated from 6-day and 19-day chick embryos and varying the extracellular sodium and potassium concentrations. The results show that for both young and old embryonic cardiac cells the resting potential depends primarily on the extracellular potassium concentration and the amplitude and rate of rise of the action potential depend primarily on the extracellular sodium concentration.

Sodium dependence of carnitine transport in isolated perfused adult rat hearts

1983 ◽  
Vol 244 (2) ◽  
pp. H247-H252 ◽  
Author(s):  
T. C. Vary ◽  
J. R. Neely
Keyword(s):  
Potassium Concentration ◽  
Sodium Concentration ◽  
Extracellular Potassium ◽  
Extracellular Potassium Concentration ◽  
Rat Hearts ◽  
Carrier Mediated Transport ◽  
Physiological Serum ◽  
Carnitine Transport ◽  
Extracellular Sodium ◽  
Carnitine Concentration

In heart muscle, the intracellular carnitine concentration is approximately 40 times higher than the plasma carnitine concentration, suggesting the existence of an active transport process. At physiological serum carnitine concentrations (44 microM), 80% of total myocardial carnitine uptake occurs via a carrier-mediated transport system. The mechanism of this carrier-mediated transport was studied in isolated perfused rat hearts. Carnitine transport showed an absolute dependence on the extracellular sodium concentration. The rate of carnitine transport was linearly related to the perfusate sodium concentration at every perfusate carnitine concentration examined (15-100 microM). Total removal of extracellular sodium completely abolished the carrier-mediated transport. Decreasing the perfusate potassium concentration from a control of 5.9 to 0.6 mM stimulated transport by 35%, whereas increasing the extracellular potassium concentration from 5.9 to 25 mM reduced transport by 60%. The carrier-mediated transport was inversely proportional to the extracellular potassium concentration. Acetylcholine (10(-3) M), isoproterenol (10(-7) M), or ouabain (10(-3) did not alter the rate of carnitine transport. Addition of tetrodotoxin (10(-5) stimulated carnitine transport by about 40%, while gramicidin S (5 X 10(-6) M) decreased uptake by about 18% relative to control. The data provide evidence that carnitine transport by cardiac cells occurs by a Na+-dependent cotransport mechanism that is dependent on the Na+ electrochemical gradient.

Metabolism and electrical activity of the heart: action of 2–4-dinitrophenol and ATP

1959 ◽  
Vol 196 (2) ◽  
pp. 377-380 ◽  
Author(s):  
Walmor Carlos de Mello
Keyword(s):  
Skeletal Muscle ◽  
Electrical Activity ◽  
Potassium Concentration ◽  
Single Cells ◽  
Sinus Node ◽  
Resting Potential ◽  
Extracellular Potassium ◽  
Perfusion Fluid ◽  
Extracellular Potassium Concentration ◽  
Diastolic Depolarization

The effects of DNP on the electrical activity of single cells of the sinus node, right auricle and A-V node, were studied with microelectrodes. It was observed that this agent caused an initial tachycardia followed by a bradycardia, a decrease in the duration of the action potential, a decrease of the resting potential and a decrease in the slope of diastolic depolarization of pacemaker tissues. A complete inhibition of the electrical activity was observed in 45 minutes after the addition of DNP to the perfusion fluid. A similar result was obtained with sodium azide. A significant recovery of the electrical activity was obtained with the use of a system with DNP and ATP. A possible increase of the extracellular potassium concentration produced by DNP similar to that observed in skeletal muscle is discussed. An incomplete loss of the resting potential observed with DNP makes it probable that at least a fraction of the resting potential is independent of the energy supplied by oxidative phosphorylation.

scholarly journals Untersuchungen über den Kaliumtransport bei Escherichia coli B / Potassium Transport in Escherichia coli B

1972 ◽  
Vol 27 (1) ◽  
pp. 62-67 ◽  
Author(s):  
G. Pilwat ◽  
U. Zimmermann
Keyword(s):  
Escherichia Coli ◽  
Potassium Concentration ◽  
Sodium Concentration ◽  
Extracellular Potassium ◽  
High Sodium ◽  
Extracellular Potassium Concentration ◽  
Intracellular Potassium ◽  
Extracellular Sodium ◽  
Escherichia Coli B ◽  
Intracellular Potassium Concentration

The stationary intracellular potassium concentration in E. coli B 525 has been studied as a function of the extracellular potassium and sodium concentrations.The ratio of extracellular to intracellular potassium concentration is shown to be a linear function of the extracellular potassium concentration if the extracellular sodium concentration is low (20 mmoles/l). In the case of high sodium concentration (100 mmoles/l) the ratio is independent of the extracellular potassium concentration if the potassium concentration is below 1,2 mmoles/l.In order to describe the distribution of potassium uniformly over the whole range of the extracellular potassium and sodium concentrations a carrier system with two sites has to be supposed.

scholarly journals The Ionic Basis of the Resting Potential in a Cross-Striated Muscle of the Aquatic Snail Lymnaea Stagnalis

1984 ◽  
Vol 108 (1) ◽  
pp. 305-314
Author(s):  
B. L. BREZDEN ◽  
D. R. GARDNER
Keyword(s):  
Membrane Potential ◽  
Lymnaea Stagnalis ◽  
Striated Muscle ◽  
Potassium Concentration ◽  
Muscle Cells ◽  
Resting Potential ◽  
Extracellular Potassium ◽  
Heart Ventricle ◽  
Sodium Permeability ◽  
Ionic Basis

The mean resting potential in the heart ventricle muscle cells of the freshwater snail Lymnaea stagnalis was found to be −61.2±3.5 (˙˙) mV (ranging from −56mV to −68mV). The average intracellular potassium concentration was estimated to be 51.5±14.6(˙˙) m (ranging from 27.8 m to 77.3 m). The membrane of the heart ventricle muscle cells appears to be permeable to both potassium and chloride, as changes in the extracellular concentration of either of these ions resulted in a change in the membrane potential. A ten-fold change in the extracellular potassium concentration was associated with a 50.4±3.8(˙˙) mV slope when the potassium concentration was above about 6 m. Deviations from the straight-line relation predicted for a potassium electrode could be accounted for by introducing a term for sodium permeability. The ionic basis of the membrane potential in these cells can be described by a modified form of the Goldman-Hodgkin- Katz equation.

Mechanism of Inhibition of Smooth Muscle Tension in Guinea-Pig Taenia Coli by Ouabain

1974 ◽  
Vol 52 (4) ◽  
pp. 898-901 ◽  
Author(s):  
D. Bose
Keyword(s):  
Guinea Pig ◽  
Muscle Tension ◽  
Sodium Concentration ◽  
Inhibitory Response ◽  
The Other ◽  
Extracellular Potassium ◽  
Taenia Coli ◽  
Mechanism Of Inhibition ◽  
Intracellular Sodium Concentration ◽  
Extracellular Sodium

Ouabain produced an increase in tension in the guinea-pig taenia coli which was abolished in the presence of high extracellular potassium. On the other hand the delayed inhibitory response of ouabain could only be abolished by the removal of extracellular sodium. The mechanism of inhibition of contraction by ouabain appears to be due to elevation of intracellular sodium concentration.

scholarly journals The Electrical Activity of Embryonic Chick Heart Cells Isolated in Tissue Culture Singly or in Interconnected Cell Sheets

1968 ◽  
Vol 52 (3) ◽  
pp. 643-665 ◽  
Author(s):  
Robert L. DeHaan ◽  
Sheldon H. Gottlieb
Keyword(s):  
Action Potential ◽  
Single Cells ◽  
Electrical Contact ◽  
Resting Potential ◽  
Heart Cells ◽  
Embryonic Chick ◽  
Irreversible Damage ◽  
Diastolic Depolarization ◽  
Chick Heart ◽  
Embryonic Chick Heart

Embryonic chick heart cells were cultured on a plastic surface in sparse sheets of 2–50 cells mutually in contact, or isolated as single cells. Conditions are described which permitted conjoint cells to be impaled with recording microelectrodes with 75% success, and isolated single cells with 8% success. It is proposed that cells in electrical contact with neighbors are protected from irreversible damage by the penetrating electrode, by a flow of ions or other substances from connected cells across low-impedance intercellular junctions. Action potentials recorded from conjoint and isolated single cells were similar in form and amplitude. The height or shape of the action potential thus appears not to depend upon spatial relationships of one cell to another. As the external potassium concentration was increased from 1.3 mM to 6 mM, cells became hyperpolarized while the afterhyperpolarization was reduced. At higher potassium levels, the afterhyperpolarization disappeared, the slope of the slow diastolic depolarization decreased, and resting potential fell along a linear curve with a slope of 61 mv per 10-fold increase in potassium. In pacemaker cells the diastolic depolarization consists of two phases: (a) recovery from the afterpotential of the previous action potential and (b) the pacemaker potential. These phases are separated by a point of inflection, and represent manifestations of different mechanisms. Evidence is presented that it is the point of inflection (PBA) rather than the point of maximal diastolic potential, that should be taken as the resting potential.

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