Sodium permeability of frog skeletal muscle in absence and presence of veratridine

1987 ◽  
Vol 252 (2) ◽  
pp. C190-C196 ◽  
Author(s):  
L. C. McKinney ◽  
R. W. Ratzlaff
Keyword(s):  
Sodium Channels ◽  
Sartorius Muscle ◽  
Constant Field ◽  
Dependent Manner ◽  
Sodium Permeability ◽  
Voltage Range ◽  
Flux Measurements ◽  
Dose Dependent ◽  
Frog Sartorius ◽  
External Ph

The effect of veratridine on the Na permeability of frog sartorius muscle was studied by means of ion flux measurements using radiolabeled sodium. Veratridine increases Na influx in a dose-dependent manner (apparent Kd = 160 +/- 7 microM when Vm congruent to -40 mV). The increase can be completely inhibited by tetrodotoxin (TTX) (apparent Ki = 8 +/- 2 nM), indicating that all veratridine-induced Na influx occurs via sodium channels. The time constant for the rate of onset of veratridine action is 1 h. Raising external pH one unit to 8.3 causes the rate of action of veratridine and the final level of Na influx to increase. The apparent Kd for veratridine depends on membrane voltage. Values obtained in 2.5 and 5 mM K Ringer (Vm congruent to -95 and -80 mV) were 579 +/- 279 and 35 +/- 8 microM, respectively. Veratridine-induced Na influx obeys the Goldman constant field flux equation and when veratridine concentration is 1 mM, sodium permeability is 1.5 X 10(-7) cm/s. This is much less than the maximum PNa (1.6 X 10(-3) cm/s) obtained from voltage-clamp measurements of peak Na conductance. Mg (52 mM) inhibits veratridine-induced influx by about half. Aspects of resting Na influx in the absence of veratridine (but in the presence of ouabain) were also characterized. Steady-state Na influx is unaffected by tetrodotoxin over the voltage range -90-0 mV, suggesting that no sodium channels are open in the resting state. Na influx is also insensitive to curare. It is linearly dependent on external sodium and larger at more negative membrane potentials.

scholarly journals Changes in the Membrane Permeability of Frog's Sartorius Muscle Fibers in Ca-Free EDTA Solution

1963 ◽  
Vol 47 (2) ◽  
pp. 379-392 ◽  
Author(s):  
H. Kimizuka ◽  
K. Koketsu
Keyword(s):  
Membrane Permeability ◽  
Chloride Content ◽  
Chloride Ions ◽  
Sartorius Muscle ◽  
Constant Field ◽  
Sodium Influx ◽  
Sodium Potassium ◽  
Edta Solution ◽  
Frog Sartorius ◽  
Sodium And Potassium

The changes in the membrane permeability to sodium, potassium, and chloride ions as well as the changes in the intracellular concentration of these ions were studied on frog sartorius muscles in Ca-free EDTA solution. It was found that the rate constants for potassium and chloride efflux became almost constant within 10 minutes in the absence of external calcium ions, that for potassium increasing to 1.5 to 2 times normal and that for chloride decreasing about one-half. The sodium influx in Ca-free EDTA solution, between 30 and 40 minutes, was about 4 times that in Ringer's solution. The intracellular sodium and potassium contents did not change appreciably but the intracellular chloride content had increased to about 4 times normal after 40 minutes. By applying the constant field theory to these results, it was concluded that (a) PCl did not change appreciably whereas PK decreased to a level that, in the interval between 10 and 40 minutes, was about one-half normal, (b) PNa increased until between 30 and 40 minutes it was about 8 times normal. The low value of the membrane potential between 30 and 40 minutes was explained in terms of the changes in the membrane permeability and the intracellular ion concentrations. The mechanism for membrane depolarization in this solution was briefly discussed.

scholarly journals Batrachotoxin-modified sodium channels from squid optic nerve in planar bilayers. Ion conduction and gating properties.

1989 ◽  
Vol 93 (1) ◽  
pp. 23-41 ◽  
Author(s):  
M I Behrens ◽  
A Oberhauser ◽  
F Bezanilla ◽  
R Latorre
Keyword(s):  
Optic Nerve ◽  
Dissociation Constant ◽  
Sodium Channels ◽  
Single Channel ◽  
Dependent Manner ◽  
Channel Conductance ◽  
Apparent Dissociation Constant ◽  
Planar Bilayers ◽  
Voltage Range ◽  
Voltage Dependent

Squid optic nerve sodium channels were characterized in planar bilayers in the presence of batrachotoxin (BTX). The channel exhibits a conductance of 20 pS in symmetrical 200 mM NaCl and behaves as a sodium electrode. The single-channel conductance saturates with increasing the concentration of sodium and the channel conductance vs. sodium concentration relation is well described by a simple rectangular hyperbola. The apparent dissociation constant of the channel for sodium is 11 mM and the maximal conductance is 23 pS. The selectivity determined from reversal potentials obtained in mixed ionic conditions is Na+ approximately Li+ greater than K+ greater than Rb+ greater than Cs+. Calcium blocks the channel in a voltage-dependent manner. Analysis of single-channel membranes showed that the probability of being open (Po) vs. voltage relation is sigmoidal with a value of 0.5 between -90 and -100 mV. The fitting of Po requires at least two closed and one open state. The apparent gating charge required to move through the whole transmembrane voltage during the closed-open transition is four to five electronic charges per channel. Distribution of open and closed times are well described by single exponentials in most of the voltage range tested and mean open and mean closed times are voltage dependent. The number of charges associated with channel closing is 1.6 electronic charges per channel. Tetrodotoxin blocked the BTX-modified channel being the blockade favored by negative voltages. The apparent dissociation constant at zero potential is 16 nM. We concluded that sodium channels from the squid optic nerve are similar to other BTX-modified channels reconstituted in bilayers and to the BTX-modified sodium channel detected in the squid giant axon.

scholarly journals RUBIDIUM AND CESIUM FLUXES IN MUSCLE AS RELATED TO THE MEMBRANE POTENTIAL

1959 ◽  
Vol 42 (5) ◽  
pp. 983-1003 ◽  
Author(s):  
Raymond A. Sjodin
Keyword(s):  
Field Theory ◽  
Membrane Potential ◽  
Low Temperatures ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Potassium Ions ◽  
Constant Field ◽  
Cesium Ions ◽  
Potassium Flux ◽  
Frog Sartorius

The reduction of membrane potential in frog sartorius muscle produced by rubidium and cesium ions has been studied over a wide concentration range and compared with depolarization occasioned by potassium ions. The constant field theory of passive flux has been used to predict the potential changes observed. The potential data suggest certain permeability coefficient ratios and these are compared with ratios obtained from flux data using radioactive tracers. The agreement of the flux with the potential data is good if account is taken of the inhibition of potassium flux which occurs in the presence of rubidium and cesium ions. A high temperature dependence has been observed for cesium influx (Q10 = 2.5) which is correlated with the observation that cesium ions depolarize very little at low temperatures. The observations suggest that cesium ions behave more like sodium ions at low temperatures and more like potassium ions at room temperature with respect to their effect on the muscle cell resting potential. The constant field theory of passive ion flux appears to be in general agreement with the experimental results observed if account is taken of the dependence of permeability coefficients on the concentrations of ions used and of possible interactions between the permeabilities of ions.

scholarly journals Voltage dependence of desensitization. Influence of calcium and activation kinetics.

1980 ◽  
Vol 75 (5) ◽  
pp. 511-529 ◽  
Author(s):  
J F Fiekers ◽  
P M Spannbauer ◽  
B Scubon-Mulieri ◽  
R L Parsons
Keyword(s):  
Voltage Dependence ◽  
Kinetic Scheme ◽  
Sartorius Muscle ◽  
Voltage Sensitivity ◽  
Voltage Range ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Frog Sartorius ◽  
Receptor Channel

The voltage dependence of carbachol-induced desensitization has been analyzed in potassium-depolarized frog sartorius muscle preparations with voltage clamp techniques over a wide voltage range (-120 to +40 mV). Desensitization developed exponentially at all voltages with tau, the time constant of desensitization onset, varying as a logarithmic function of membrane voltage. The voltage dependence of tau remained in calcium-deficient solutions and was not altered by elevating either the level of extracellular or intracellular calcium. We have analyzed our results according to a simple sequential kinetic scheme in which the rate-limiting step in the development of desensitization is a transition of the receptor channel complex from the activated conducting state to a desensitized, nonconducting state. We conclude (a) that the observed voltage sensitivity of desensitization primarily resides in the voltage dependence of this transition, and (b) the kinetics of activation appear to have a greater influence on the observed rate of desensitization than on its voltage dependence. The magnitude of the voltage dependence suggests that a greater change in free energy is required for the transition to the desensitized state than for the transition between the open and closed states of the receptor channel complex.

Initiation of the cortical reaction in hamster and sheep oocytes in response to inositol trisphosphate

1988 ◽  
Vol 91 (1) ◽  
pp. 139-144
Author(s):  
D.G. Cran ◽  
R.M. Moor ◽  
R.F. Irvine
Keyword(s):  
External Medium ◽  
Cortical Granule ◽  
Dependent Manner ◽  
Cortical Granules ◽  
Cortical Reaction ◽  
Ph Dependent ◽  
Cortical Granule Exocytosis ◽  
Gamma S ◽  
Dose Dependent ◽  
External Ph

Microinjection of inositol 1,4,5-triphosphate into sheep and hamster oocytes induces secretion of cortical granules in a dose-dependent manner. In the sheep, this effect is strongly pH-dependent with minimal exocytosis taking place at pH 6.8 but a full cortical reaction occurring at pH8.0. Exocytosis in the hamster is also affected by the pH of the external medium but to a lesser extent. Injection of GTP gamma S also induces exocytosis in both species but is more effective in the hamster. It is suggested that inositol metabolism stimulated by sperm-egg interaction with a GTP-binding protein may be part of the mechanism leading to cortical granule exocytosis and that this may be modulated by the external pH.

Effects of amphotericin B on the electrical properties and electrolyte content of frog sartorius muscle

1980 ◽  
Vol 58 (9) ◽  
pp. 1138-1141 ◽  
Author(s):  
A. Coulombe ◽  
O. F. Schanne ◽  
I. Reisin ◽  
E. Ruiz-Ceretti
Keyword(s):  
Membrane Potential ◽  
Amphotericin B ◽  
Membrane Resistance ◽  
Equilibrium Potential ◽  
Sartorius Muscle ◽  
Sodium Permeability ◽  
A Value ◽  
Goldman Equation ◽  
Frog Sartorius ◽  
B 52

We studied the effect of amphotericin B (52 μM) on the membrane potential, membrane resistance, and intracellular Na+ and K+ concentrations in isolated frog sartorius muscles to characterize further the nature of the ionic conductance induced by the antibiotic. After 5 h of exposure to amphotericin B, the membrane depolarized from −89.9 to −51.0 mV, the membrane resistance decreased from 4537 to 907 Ωcm2, [K]i decreased from 122 to 31.2 mmol/L fiber H2O, and [Na]i increased from 30.9 to 88.7 mmol/L fiber H2O. The relative sodium permeability, PNa/PK, calculated with the Goldman equation remained apparently constant at a value of 0.01 in treated and untreated muscles. We hypothesize that amphotericin B creates either a nonselective cation channel or a completely nonselective ionic leak channel whose equilibrium potential is equal or close to the membrane potential.

Effects of Low Molecular Weight Heparin and Unfragmented Heparin on Induction of Osteoporosis in Rats

1990 ◽  
Vol 63 (03) ◽  
pp. 505-509 ◽  
Author(s):  
Thomas Mätzsch ◽  
David Bergqvist ◽  
Ulla Hedner ◽  
Bo Nilsson ◽  
Per Østergaar
Keyword(s):  
Molecular Weight ◽  
Bone Mineral ◽  
Low Molecular Weight Heparin ◽  
Zinc Content ◽  
Low Molecular Weight ◽  
Dependent Manner ◽  
Bone Mineral Mass ◽  
Bone Ash ◽  
Dose Dependent ◽  
Mineral Mass

SummaryA comparison between the effect of low molecular weight heparin (LMWH) and unfragmented heparin (UH) on induction of osteoporosis was made in 60 rats treated with either UH (2 IU/ g b w), LMWH in 2 doses (2 Xal U/g or 0.4 Xal U/g) or placebo (saline) for 34 days. Studied variables were: bone mineral mass in femora; fragility of humera; zinc and calcium levels in serum and bone ash and albumin in plasma. A significant reduction in bone mineral mass was found in all heparin-treated rats. There was no difference between UH and LMWH in this respect. The effect was dose-dependent in LMWH-treated animals. The zinc contents in bone ash were decreased in all heparin-treated rats as compared with controls. No recognizable pattern was seen in alterations of zinc or calcium in serum. The fragility of the humera, tested as breaking strength did not differ between treatment groups and controls. In conclusion, if dosed according to similar factor Xa inhibitory activities, LMWH induces osteoporosis to the same extent as UH and in a dose-dependent manner. The zinc content in bone ash was decreased after heparin treatment, irrespective of type of heparin given.

Effects of NO-Donors on Thrombus Formation and Microcirculation in Cerebral Vessels of the Rat

1996 ◽  
Vol 76 (01) ◽  
pp. 111-117 ◽  
Author(s):  
Yasuto Sasaki ◽  
Junji Seki ◽  
John C Giddings ◽  
Junichiro Yamamoto
Keyword(s):  
Blood Flow ◽  
Thrombus Formation ◽  
Dependent Manner ◽  
Red Cell ◽  
Cell Velocity ◽  
Red Cell Velocity ◽  
The Mean ◽  
Wall Shear ◽  
Dose Dependent

SummarySodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), are known to liberate nitric oxide (NO). In this study the effects of SNP and SIN-1 on thrombus formation in rat cerebral arterioles and venules in vivo were assessed using a helium-neon (He-Ne) laser. SNP infused at doses from 10 Μg/kg/h significantly inhibited thrombus formation in a dose dependent manner. This inhibition of thrombus formation was suppressed by methylene blue. SIN-1 at a dose of 100 Μg/kg/h also demonstrated a significant antithrombotic effect. Moreover, treatment with SNP increased vessel diameter in a dose dependent manner and enhanced the mean red cell velocity measured with a fiber-optic laser-Doppler anemometer microscope (FLDAM). Blood flow, calculated from the mean red cell velocity and vessel diameters was increased significantly during infusion. In contrast, mean wall shear rates in the arterioles and venules were not changed by SNP infusion. The results indicated that SNP and SIN-1 possessed potent antithrombotic activities, whilst SNP increased cerebral blood flow without changing wall shear rate. The findings suggest that the NO released by SNP and SIN-1 may be beneficial for the treatment and protection of cerebral infarction

Melatonin actions in the heart; more than a hormone

2018 ◽  
Vol 1 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Darío Acuña-Castroviejo ◽  
Maria T Noguiera-Navarro ◽  
Russel J Reiter ◽  
Germaine Escames
Keyword(s):  
Cell Membranes ◽  
Myocardial Cell ◽  
Rat Tissues ◽  
Dependent Manner ◽  
Broad Distribution ◽  
Multiple Organs ◽  
High Doses ◽  
Extrapineal Melatonin ◽  
Dose Dependent ◽  
Different Doses

Due to the broad distribution of extrapineal melatonin in multiple organs and tissues, we analyzed the presence and subcellular distribution of the indoleamine in the heart of rats. Groups of sham-operated and pinealectomized rats were sacrificed at different times along the day, and the melatonin content in myocardial cell membranes, cytosol, nuclei and mitochondria, were measured. Other groups of control animals were treated with different doses of melatonin to monitor its intracellular distribution. The results show that melatonin levels in the cell membrane, cytosol, nucleus, and mitochondria vary along the day, without showing a circadian rhythm. Pinealectomized animals trend to show higher values than sham-operated rats. Exogenous administration of melatonin yields its accumulation in a dose-dependent manner in all subcellular compartments analyzed, with maximal concentrations found in cell membranes at doses of 200 mg/kg bw melatonin. Interestingly, at dose of 40 mg/kg b.w, maximal concentration of melatonin was reached in the nucleus and mitochondrion. The results confirm previous data in other rat tissues including liver and brain, and support that melatonin is not uniformly distributed in the cell, whereas high doses of melatonin may be required for therapeutic purposes.

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