scholarly journals Prolonged action potential of frog skeletal muscle membrane in Ca-free EGTA solution.

1983 ◽  
Vol 33 (5) ◽  
pp. 777-788 ◽  
Author(s):  
Shoichi MINOTA ◽  
Kyozo KOKETSU
Keyword(s):  
Skeletal Muscle ◽  
Action Potential ◽  
Muscle Membrane ◽  
Frog Skeletal Muscle ◽  
Prolonged Action

The Effect of Lanthanum on Excitation–Contraction Coupling in Frog Skeletal Muscle

1974 ◽  
Vol 52 (6) ◽  
pp. 1126-1135 ◽  
Author(s):  
D. J. Parry ◽  
A. Kover ◽  
G. B. Frank
Keyword(s):  
Skeletal Muscle ◽  
Action Potential ◽  
Muscle Membrane ◽  
Frog Skeletal Muscle ◽  
Tension Development ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Reduced Rate ◽  
Caffeine Contractures

Exposure of frog toe muscles to 1 mM La3+ results in a decrease in amplitude and rate of tension development of potassium contractures and twitches. At this concentration La3+ also inhibits the uptake of calcium, both in the resting condition and during stimulation. Caffeine contractures are unaffected even after a 5-min pre-exposure to La3+. The depolarization induced by various concentrations of K+ is reduced by about 10 mV as is the amplitude of the action potential. The rate of rise of the action potential is reduced by about 40% after 1 min in La3+ Ringer. Neither the decreased amplitude nor the reduced rate of depolarization is considered to be sufficient to explain the inhibition of tension development. It is suggested that La3+ partially uncouples excitation from contraction by preventing the release of a trigger-Ca2+ fraction from some site on the muscle membrane. This fraction normally plays a role in excitation–contraction coupling, although some tension may still be developed in the absence of a trigger-Ca2+ influx.

Membrane domain localization of pH-regulating transporters in frog skeletal muscle membrane vesicles

1996 ◽  
Vol 271 (4) ◽  
pp. C1367-C1379 ◽  
Author(s):  
R. W. Putnam ◽  
P. B. Douglas ◽  
N. A. Ritucci
Keyword(s):  
Skeletal Muscle ◽  
Atpase Activity ◽  
Surface Membrane ◽  
Membrane Vesicles ◽  
Muscle Membrane ◽  
Frog Skeletal Muscle ◽  
Membrane Domain ◽  
Ph Response ◽  
Kinase C ◽  
Inside Out

The distribution of pH-regulating transporters in surface and transverse (T) tubular membrane (TTM) domains of frog skeletal muscle was studied. 2',7'-Bis(carboxyethyl)-5(6)- carboxyfluorescein-loaded giant sarcolemmal vesicles, containing surface membrane, exhibited reversible Na+/H+ exchange. A microsomal vesicle fraction was shown to be enriched in TTM on the basis of high Na(+)-K(+)-ATPase and Mg(2+)-ATPase activity, high ouabain and nitrendipine binding, and low Ca(2+)-ATPase activity. TTM vesicles were well sealed and oriented inside out. Vesicles were loaded with the pH-sensitive dye pyranine. In response to an inwardly directed Na+ gradient, vesicles displayed virtually no alkalinization unless monensin was present. No pH response to an imposed Na+ gradient was seen regardless of the direction of the pH gradient across the vesicles, after phosphorylation of the vesicles with protein kinase C, or when exposed to guanosine 5'-O-(3-thiotriphosphate). In the presence of CO2, addition of Na+ or Cl- had no effect on vesicle pH. These data indicate that the TTM lacks functional pH-regulating transporters [Na+/H+ and (Na+ + HCO3-)/Cl- exchangers], suggesting that pH-regulating transporters are localized only to the surface membrane domain in frog muscle.

High-affinity [3H]PN200-110 and [3H]ryanodine binding to rabbit and frog skeletal muscle

1994 ◽  
Vol 266 (2) ◽  
pp. C462-C466 ◽  
Author(s):  
K. Anderson ◽  
A. H. Cohn ◽  
G. Meissner
Keyword(s):  
Skeletal Muscle ◽  
Rabbit Skeletal Muscle ◽  
Muscle Membrane ◽  
Scatchard Analysis ◽  
Physical Interaction ◽  
Frog Skeletal Muscle ◽  
Release Channel ◽  
High Affinity ◽  
Voltage Dependent ◽  
Student’S T

In vertebrate skeletal muscle, the voltage-dependent mechanism of sarcoplasmic reticulum (SR) Ca2+ release, commonly referred to as excitation-contraction (E-C) coupling, is mediated by the voltage-sensing dihydropyridine receptor (DHPR), which is believed to affect SR Ca2+ release through a physical interaction with the SR ryanodine receptor (RYR)/Ca2+ release channel. Scatchard analysis of ligand binding of [3H]PN200-110 to the DHPR and [3H]ryanodine to the RYR indicated the presence of high-affinity sites in muscle homogenates, with maximum binding (Bmax) values of 72 +/- 26 and 76 +/- 30 pmol/g wet wt for rabbit skeletal muscle, and 27 +/- 14 and 44 +/- 13 pmol/g wet wt for frog skeletal muscle, respectively. The Bmax values corresponded to a PN200-110-to-ryanodine binding ratio of 0.98 +/- 0.26 and 0.61 +/- 0.24 for rabbit and frog skeletal muscle, respectively, and were found by Student's t test to be significantly different (P < 0.02, n = 7). These results are compared with measurements with isolated rabbit skeletal muscle membrane fractions and discussed in relation to our current understanding of the mechanism of E-C coupling in skeletal muscle.

scholarly journals Model of Sarcomeric Ca2+ Movements, Including ATP Ca2+ Binding and Diffusion, during Activation of Frog Skeletal Muscle

1998 ◽  
Vol 112 (3) ◽  
pp. 297-316 ◽  
Author(s):  
S.M. Baylor ◽  
S. Hollingworth
Keyword(s):  
Skeletal Muscle ◽  
Action Potential ◽  
Metal Binding ◽  
Time Course ◽  
Current Knowledge ◽  
Diffusion Constant ◽  
Compartment Model ◽  
Half Width ◽  
Frog Skeletal Muscle ◽  
And Diffusion

Cannell and Allen (1984. Biophys. J. 45:913–925) introduced the use of a multi-compartment model to estimate the time course of spread of calcium ions (Ca2+) within a half sarcomere of a frog skeletal muscle fiber activated by an action potential. Under the assumption that the sites of sarcoplasmic reticulum (SR) Ca2+ release are located radially around each myofibril at the Z line, their model calculated the spread of released Ca2+ both along and into the half sarcomere. During diffusion, Ca2+ was assumed to react with metal-binding sites on parvalbumin (a diffusible Ca2+- and Mg2+-binding protein) as well as with fixed sites on troponin. We have developed a similar model, but with several modifications that reflect current knowledge of the myoplasmic environment and SR Ca2+ release. We use a myoplasmic diffusion constant for free Ca2+ that is twofold smaller and an SR Ca2+ release function in response to an action potential that is threefold briefer than used previously. Additionally, our model includes the effects of Ca2+ and Mg2+ binding by adenosine 5′-triphosphate (ATP) and the diffusion of Ca2+-bound ATP (CaATP). Under the assumption that the total myoplasmic concentration of ATP is 8 mM and that the amplitude of SR Ca2+ release is sufficient to drive the peak change in free [Ca2+] (Δ[Ca2+]) to 18 μM (the approximate spatially averaged value that is observed experimentally), our model calculates that (a) the spatially averaged peak increase in [CaATP] is 64 μM; (b) the peak saturation of troponin with Ca2+ is high along the entire thin filament; and (c) the half-width of Δ[Ca2+] is consistent with that observed experimentally. Without ATP, the calculated half-width of spatially averaged Δ[Ca2+] is abnormally brief, and troponin saturation away from the release sites is markedly reduced. We conclude that Ca2+ binding by ATP and diffusion of CaATP make important contributions to the determination of the amplitude and the time course of Δ[Ca2+].

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