scholarly journals Delayed Rectification and Anomalous Rectification in Frog's Skeletal Muscle Membrane

1962 ◽  
Vol 46 (1) ◽  
pp. 97-115 ◽  
Author(s):  
Shigehiro Nakajima ◽  
Shizuko Iwasaki ◽  
Kunihiko Obata
Keyword(s):  
Skeletal Muscles ◽  
Potassium Conductance ◽  
Muscle Membrane ◽  
Transient Phenomenon ◽  
Depolarization Current ◽  
Ringer’S Solution ◽  
Anomalous Rectification ◽  
Potassium Inactivation ◽  
Delayed Rectification ◽  
Current Voltage

Delayed rectification was elicited in frog's skeletal muscles bathed in choline-Ringer's solution, in normal Ringer's solution with tetrodotoxin, in 40 mM Na2SO4 solution with tetrodotoxin, and even in 40 mM K2SO4 solution when the membrane had been previously hyperpolarized. However, after a sustained depolarization current-voltage relations in 40 mM K2SO4 and in 40 mM Na2SO4 solutions revealed a rectifier property in the anomalous direction. This indicates that the increase in potassium conductance which is brought about upon depolarization is a transient phenomenon and is inactivated by a maintained depolarization, and that this potassium inactivation process converts the delayed rectification into the anomalous rectification. In normal Ringer's solution with tetrodotoxin and in the 40 mM Na2SO4 solution with tetrodotoxin the apparent resistance was increased when the membrane was hyperpolarized beyond about -150 mv. This is thought to be due to a decrease of K conductance caused by a strong hyperpolarizing current. In the 40 mM Na2SO4 solution with tetrodotoxin a de- or hyperpolarizing current pulse induced a prolonged depolarizing response. During the early phase of this response the effective resistance was lower, and during the following phase greater than that in the resting fiber. An interpretation in terms of the ionic hypothesis was made of the nature of this response.

Characteristics of skeletal muscle ecto-ATPase in situ

1984 ◽  
Vol 62 (10) ◽  
pp. 1015-1026 ◽  
Author(s):  
J. F. Manery ◽  
E. E. Dryden ◽  
J. S. Still ◽  
G. Madapallimattam
Keyword(s):  
Skeletal Muscles ◽  
Divalent Cations ◽  
Maximum Activity ◽  
Ruthenium Red ◽  
Muscle Membrane ◽  
Ringer’S Solution ◽  
A Cell ◽  
Membrane Bound ◽  
Mitochondrial Origin

The properties of a cell surface nucleoside 5′-triphosphatase have been studied in small, intact, frog skeletal muscles, as a means of distinguishing the enzyme from other adenosine 5′-triphosphatases and of understanding its behaviour in the muscle membrane. The ectoenzyme in situ was shown to be a Ca2+- or Mg2+-activated ATPase liberating 7.5 ± 0.4 (mean ± SEM, n = 30) μmol of inorganic phosphate/g of muscle per 20 min, when the muscle was exposed to 2 mM ATP and 2 mM Ca2+ in Ringer's solution. The apparent Km for Mg2+ was 0.74 mM and for Ca2+ was 0.23 mM. A residual ATPase activity (20%) was found in the complete absence of divalent cations suggesting the existence of two ATPase types. A broad specificity toward nucleoside 5′-triphosphates was exhibited by the ecto-ATPase, but there was no nonspecific phosphatase activity. The enzyme was inhibited by La3+ and Cd2+, but was insensitive to ouabain, 2,4-dinitrophenol, oligomycin, and ruthenium red. Thus the ectoenzyme was not a Na+,K+-transport ATPase, was not an ATPase of mitochondrial origin, or a Ca2+-transport enzyme. Insulin had no effect. Inhibition by mersalyl, carbodiimide, and polar and cross-linking nonpolar nitrobenzene derivatives suggested that, for maximum activity, this membrane-bound enzyme required free sulfhydryl groups, certain free carboxyls, and an appreciable degree of hydrophobicity in its microenvironment.

scholarly journals Delayed Rectification and Anomalous Rectification in Skeletal Muscle Membrane

1961 ◽  
Vol 37 (8) ◽  
pp. 505-508 ◽  
Author(s):  
Shigehiro NAKAJIMA ◽  
Shizuko IWASAKI ◽  
Kunihiko OBATA
Keyword(s):  
Skeletal Muscle ◽  
Muscle Membrane ◽  
Anomalous Rectification ◽  
Delayed Rectification

The effect of ionophore A23178 on the α-actinin crosslinks in the z-band of frog skeletal muscle: An EM study

1986 ◽  
Vol 44 ◽  
pp. 154-155
Author(s):  
F.T. Llados ◽  
V. Krlho ◽  
G.D. Pappas
Keyword(s):  
Muscle Damage ◽  
Transmitter Release ◽  
Skeletal Muscles ◽  
Calcium Uptake ◽  
Muscle Membrane ◽  
Frog Skeletal Muscle ◽  
Ach Release ◽  
Sustained Action ◽  
Calcium Deposits ◽  
Intense Stimulation

It Is known that Ca++ enters the muscle fiber at the junctional area during the action of the neurotransmitter, acetylcholine (ACh). Pappas and Rose demonstrated that following Intense stimulation, calcium deposits are found In the postsynaptic muscle membrane, Indicating the existence of calcium uptake In the postsynaptic area following ACh release. In addition to this calcium uptake, when mammal Ian skeletal muscles are exposed to a sustained action of the neurotransmitter, muscle damage develops. These same effects, l.e., Increased transmitter release, calcium uptake and finally muscle damage, can be obtained by Incubating the muscle with lonophore A23178.

scholarly journals Action Potentials in Rhodnius Oocytes: Repolarization is Sensitive to Potassium Channel Blockers

1986 ◽  
Vol 126 (1) ◽  
pp. 119-132
Author(s):  
M. J. O'DONNELL
Keyword(s):  
Potassium Channel ◽  
Action Potentials ◽  
Potassium Conductance ◽  
Channel Blockers ◽  
Calcium Dependent ◽  
Outward Rectification ◽  
Current Voltage ◽  
Potassium Channel Blockers ◽  
Potassium Conductances ◽  
Voltage Dependent

Depolarization of Rhodnius oocytes evokes action potentials (APs) whose rising phase is calcium-dependent. The ionic basis for the repolarizing (i.e. falling) phase of the AP was examined. Addition of potassium channel blockers (tetraethylammonium, tetrabutylammonium, 4-aminopyridine, atropine) to the bathing saline increased the duration and overshoot of APs. Intracellular injection of tetraethyl ammonium had similar effects. These results suggest that a voltage-dependent potassium conductance normally contributes to repolarization. Repolarization does not require a chloride influx, because substitution of impermeant anions for chloride did not increase AP duration. AP duration and overshoot actually decreased progressively when chloride levels were reduced. Current/voltage curves show inward and outward rectification, properties often associated with potassium conductances. Outward rectification was largely blocked by external tetraethylammonium. Possible functions of the rectifying properties of the oocyte membrane are discussed.

Two types of K+ channels at the basolateral membrane of proximal tubule: inhibitory effect of taurine

1999 ◽  
Vol 277 (2) ◽  
pp. F290-F297 ◽  
Author(s):  
Jean-François Noulin ◽  
Emmanuelle Brochiero ◽  
Jean-Yves Lapointe ◽  
Raynald Laprade
Keyword(s):  
Potassium Channels ◽  
Time Constant ◽  
Potassium Conductance ◽  
Single Type ◽  
K Channel ◽  
Open Probability ◽  
Open Time ◽  
Voltage Curve ◽  
Current Voltage ◽  
Current Voltage Curve

The cell-attached configuration of the patch-clamp technique was used to investigate the effects of taurine on the basolateral potassium channels of rabbit proximal convoluted tubule. In the absence of taurine, the previously reported ATP-blockable channel, KATP, was observed in 51% of patches. It is characterized by an inwardly rectifying current-voltage curve with an inward slope conductance of 49 ± 5 pS ( n = 15) and an outward slope conductance of 13 ± 6 pS ( n = 15). The KATP channel open probability ( P o) is low, 0.15 ± 0.06 ( n = 15) at a − V p = −100 mV ( V pis the pipette potential), and increases slightly with depolarization. The gating kinetics are characterized by one open time constant (τo = 5.0 ± 1.9 ms, n = 6) and two closed time constants (τC1 = 5.2 ± 1.5 ms, τC2 = 140 ± 40 ms; n = 6). In 34% of patches, a second type of potassium channel, sK, with distinct properties was recorded. Its current-voltage curve is characterized by a sigmoidal shape, with an inward slope conductance of 12 ± 2 pS ( n = 4). Its P o is voltage independent and averages 0.67 ± 0.03 ( n = 4) at − V p = −80 mV. Both its open time and closed time distributions are described by a single time constant (τo = 96 ± 19 ms, τC = 10.5 ± 3.6 ms; n = 4). Extracellular perfusion of 40 mM taurine fails to affect sK channels, whereas KATP channel P o decreases by 75% (from 0.17 ± 0.06 to 0.04 ± 0.02, n = 7, P < 0.05). In conclusion, the absolute basolateral potassium conductance of rabbit proximal tubules is the resulting combination of, at least, two types of potassium channels of roughly equal importance: a high-conductance low-open probability KATP channel and a low-conductance high-open probability sK channel. The previously described decrease in the basolateral absolute potassium conductance by taurine is, however, mediated by a single type of K channel: the ATP-blockable K channel.

scholarly journals Magnitude and location of surface charges on Myxicola giant axons.

1975 ◽  
Vol 66 (1) ◽  
pp. 47-65 ◽  
Author(s):  
T Begenisich
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Potassium Conductance ◽  
Electronic Charge ◽  
Surface Charges ◽  
Giant Axons ◽  
Current Voltage ◽  
Instantaneous Current ◽  
Sodium And Potassium

The effects of changes in the concentration of calcium in solutions bathing Myxicola giant axons on the voltage dependence of sodium and potassium conductance and on the instantaneous sodium and potassium current-voltage relations have been measured. The sodium conductance-voltage relation is shifted along the voltage axis by 13 mV in the hyperpolarizing direction for a fourfold decrease in calcium concentration. The potassium conductance-voltage relation is shifted only half as much as that for sodium. There is no effect on the shape of the sodium and potassium instantaneous current-voltage curves: the normal constant-field rectification of potassium currents is maintained and the normal linear relationship of sodium currents is maintained. Considering that shifts in conductances would reflect the presence of surface charges near the gating machinery and that shape changes of instantaneous current-voltage curves would reflect the presence of surface charges near the ionic pores, these results indicate a negative surface charge density of about 1 electronic charge per 120 A2 near the sodium gating machinery, about 1 e/300 A2 for the potassium gating machinery, and much less surface charge near the sodium or potassium pores. There may be some specific binding of calcium to these surface charges with an upper limit on the binding constant of about 0.2 M-1. The differences in surface charge density suggest a spatial separation for these four membrane components.

Mechanism of long-lasting synaptic inhibition in Aplysia neuron R15

1980 ◽  
Vol 44 (6) ◽  
pp. 1148-1160 ◽  
Author(s):  
W. B. Adams ◽  
I. Parnas ◽  
I. B. Levitan
Keyword(s):  
Action Potentials ◽  
Potassium Conductance ◽  
Reversal Potential ◽  
Short Exposure ◽  
Ion Conductance ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Aplysia Neuron ◽  
Reversible Component ◽  
Stimulation Of

1. Long-lasting inhibition is a synaptically mediated response found in certain molluscan nerve cells that fire action potentials in bursts. It is elicited by repetitive stimulation of a presynaptic nerve and may last for minutes or hours after stimulation. 2. Voltage-clamp techniques were employed to measure the voltage dependence of the synaptically elicited current. Current-voltage curves were obtained by stepping or sweeping the voltage over the range -40 to -120 mV. 3. Long-lasting inhibition was found to be mediated by two separate conductance mechanisms. A component that reverses near -80 mV is most prominent at times up to 5 min following stimulation. A component with no reversal potential between -40 and -120 mV predominates at later times. 4. The reversible component is attenuated by reducing the intensity of stimulation of the presynaptic nerve, by injection of TEA into the postsynaptic cell, or by activation of a potassium conductance with serotonin prior to stimulation of the nerve. Thus, the reversible component appears to be mediated by an increase in potassium conductance. 5. The effects of the nonreversible component measured in the soma appear to be too large to attribute it to a conductance change that is electrically "distant" from the soma. It is attenuated by turning off a resting inward ion conductance with dopamine prior to stimulation of the nerve. It is not affected by short exposure to ouabain, but is attenuated by longer exposures that reduce the sodium and calcium gradients. Thus, the nonreversible component may be mediated by a decrease in voltage-dependent inward current flow carried by sodium or calcium.

scholarly journals Voltage Clamp Experiments on Single Muscle Fibers of Rana pipiens

1972 ◽  
Vol 60 (1) ◽  
pp. 1-19 ◽  
Author(s):  
L. E. Moore
Keyword(s):  
Voltage Clamp ◽  
Rana Pipiens ◽  
Muscle Fibers ◽  
Petroleum Jelly ◽  
Single Muscle ◽  
Transverse Tubular System ◽  
Anomalous Rectification ◽  
Outward Currents ◽  
Delayed Rectification ◽  
Tubular System

A voltage clamp for single muscle fibers has been developed. Stability of the system was achieved when an artificial node was created by enclosing a single muscle fiber in a petroleum jelly seal which served as an analogue of the myelin sheath. Typical voltage clamp records were obtained with large inward transient currents followed by a delayed rectification of the outward currents. These currents looked qualitatively similar when the transverse tubular system was destroyed. Errors in current measurement, especially those due to anomalous rectification, are discussed.

Sign in / Sign up

Export Citation Format

Share Document