Time course of calcium release and removal in skeletal muscle fibers

Melzer, Werner; Rı́os, Eduardo; Schneider, Martin F.

doi:10.1016/s0006-3495(84)84203-4

Cited by 153 publications

(217 citation statements)

References 12 publications

Supporting

Mentioning

198

Contrasting

Order By: Relevance

“…At early times after a strong depolarization, when Ca is binding in a saturating manner to Ca-free troponin and Ca, Mg-free pan, albumin, this approximation may be overly simple. Nonetheless, as shown by Melzer et al (1984), it can produce reasonable estimates of SR Ca release and, for this reason, is considered to be a reasonable assumption here, at least during the early phase of SR Ca release. At later times, however, as the value of bulk myoplasmic free [Ca] becomes large and the rapidly equilibrating Ca buffers become saturated with Ca, the value of the proportionality constant is expected to change.…”

Section: Qualitative Agreement Between the Experimental Results And Tmentioning

confidence: 76%

“…Melzer et al (1984) used this proportionality to describe in a simple fashion the properties of the rapidly equilibrating Ca buffers in myoplasm in fibers equilibrated with only 0.1 mM EGTA. At early times after a strong depolarization, when Ca is binding in a saturating manner to Ca-free troponin and Ca, Mg-free pan, albumin, this approximation may be overly simple.…”

Section: Qualitative Agreement Between the Experimental Results And Tmentioning

confidence: 99%

“…According to this scheme, an SR Ca channel is able to pass Ca ions if the receptor is in state R or CaR but not if it is in state CAR*, the inactivated state. Melzer et al (1984) and Schneider and Simon (1988) observed that, during a step depolarization, the apparent rate constant for the decrease in dA [CaT]/dt from its peak to its quasi-steady level is independent of voltage and of the value of free [Ca], at least at voltages between -40 and 0 mV. Schneider and Simon (1988) introduced Scheme I to explain this observation.…”

Section: F (T) = A(t) B(t)mentioning

confidence: 99%

See 2 more Smart Citations

Calcium inactivation of calcium release in frog cut muscle fibers that contain millimolar EGTA or Fura-2.

Jong

Pape

Baylor

et al. 1995

The Journal of General Physiology

110

View full text Add to dashboard Cite

Cut muscle fibers from Rana teraporaria (sarcomere length, 3.4-4.2 p.m) were mounted in a double and equilibrated with end-pool solutions that contained 20 mM EGTA and 1.76 mM Ca. Sarcoplasmic reticulum (SR) Ca release was estimated from changes in pH (Pape, P. C., D.-S.Jong, and W. I~ Chandler. 1995.Journal of GeneralPhysiology. 106:000-000). Although the amplitude and duration of the [Ca] transient, as well as its spatial spread from the release sites, are reduced by EGTA, SR Ca release elicited by either depolarizing voltage-clamp pulses or action potentials behaved in a manner consistent with Ca inactivation of Ca release. After a step depolarization to -20 or 10 mV, the rate of SR Ca release, corrected for SR Ca depletion, reached a peak value within 5-15 ms and then rapidly decreased to a quasi-steady level that was about half the peak value; the time constant of the last half of the decrease was usually 2--4 ms. Immediately after an action potential or a 10-15 ms prepulse to -20 mV, the peak rate of SR Ca release elicited by a second stimulation, as well as the fractional amount of release, were substantially decreased. The rising phase of the rate of release was also reduced, suggesting that at least 0.9 of the ability of the SR to release Ca had been inactivated by the first stimulation. There was little change in intramembranous charge movement, suggesting that the changes in SR Ca release were not caused by changes in its voltage activation. These effects of a first stimulation on the rate of SR Ca release elicited by a second stimulation recovered during repolarization to -90 mV; the time constant of recovery was ~25 ms in the action-potential experiments and ~50 ms in the voltage-clamp experiments. Fura-2, which is able to bind Ca more rapidly than EGTA and hence reduce the amplitude of the [Ca] transient and its spatial spread from release sites by a greater amount, did not prevent Ca inactivation of Ca release, even at con-

show abstract

Section: Qualitative Agreement Between the Experimental Results And Tmentioning

confidence: 76%

Section: Qualitative Agreement Between the Experimental Results And Tmentioning

confidence: 99%

Section: F (T) = A(t) B(t)mentioning

confidence: 99%

See 1 more Smart Citation

Calcium inactivation of calcium release in frog cut muscle fibers that contain millimolar EGTA or Fura-2.

Jong

Pape

Baylor

et al. 1995

The Journal of General Physiology

110

View full text Add to dashboard Cite

show abstract

“…A second advantage is that the estimate of SR Ca release is direct and independent of the properties of the various intrinsic myoplasmic Ca buffers. In most of the methods first used to estimate SR Ca release (Baylor et al, 1983;Melzer, Rfos, andSchneider, 1984, 1987;Klein, Simon, and Schneider, 1990), free [Ca] transients were used to calculate the concentration of Ca that was expected to have been bound by the intrinsic myoplasmic Ca buffers. The total amount of myoplasmic [Ca], free and bound, was then taken as an estimate of the amount of Ca released from the SR. A third advantage of the EGTA-phenol red method is that it is extremely sensitive.…”

Section: Introductionmentioning

confidence: 99%

Calcium release and its voltage dependence in frog cut muscle fibers equilibrated with 20 mM EGTA.

Pape

Jong

Chandler

1995

The Journal of General Physiology

129

295

View full text Add to dashboard Cite

Sarcoplasmic reticulum (SR) Ca release was studied at 13-16~ in cut fibers (sarcomere length, 3.4-3.9 I~m) mounted in a double Vaseline-gap chamber. The amplitude and duration of the action-potential stimulated free [Ca] transient were reduced by equilibration with end-pool solutions that contained 20 mM EGTA with 1.76 mM Ca and 0.63 mM phenol red, a maneuver that appeared to markedly reduce the amount of Ca complexed by troponin. A theoretical analysis shows that, under these conditions, the increase in myoplasmic free [Ca] is expected to be restricted to within a few hundred nanometers of the SR Ca release sites and to have a time course that essentially matches that of release. Furthermore, almost all of the Ca that is released from the SR is expected to be rapidly bound by EGTA and exchanged for protons with a 1:2 stoichiometry. Consequently, the time course of SR Ca release can be estimated by scaling the ApH signal measured with phenol red by -13/2. The value of 13, the buffering power of myoplasm, was determined in fibers equilibrated with a combination of EGTA, phenol red, and fura-2; its mean value was 22 mM/pH unit. The Ca content of the SR (expressed as myoplasmic concentration) was estimated from the total amount of Ca released by either a train of action potentials or a depleting voltage step; its mean value was 2,685 I~M in the action-potential experiments and 2,544 IxM in the voltage-clamp experiments. An action potential released, on average, 0.14 of the SR Ca content with a peak rate of release of,'~5 %/ms. A second action potential, elicited 20 ms later, released only 0.6 times as much Ca (expressed as a fraction of the SR content), probably because Ca inactivation of Ca release was produced by the first action potential. During a depolarizing voltage step to 60 mV, the rate of Ca release rapidly increased to a peak value of~3 %/ms and then decreased to a quasi-steady level that was only 0.6 times as large; this decrease was also probably due to Ca inactivation of Ca release. SR Ca release was studied with small step depolarizations that open no more than one SR Ca channel in 7

show abstract

“…The present studies were carried out with lower concentrations of tetracaine than used in the classical studies. The use of these lower concentrations allowed us to demonstrate that the two components of calcium release flux, the inactivating peak and the maintained steady level (Melzer, Rios & Schneider, 1984), have different sensitivities to tetracaine. We also provide evidence of an intracellular site of action of the drug.…”

Section: Introductionmentioning

confidence: 99%

Differential effects of tetracaine on two kinetic components of calcium release in frog skeletal muscle fibres.

Pizarro

Csernoch

Uribe

et al. 1992

The Journal of Physiology

View full text Add to dashboard Cite

SUMMARY1. Intramembrane charge movements and changes in intracellular calcium concentration were recorded simultaneously in voltage clamped cut skeletal muscle fibres of the frog in the presence and absence of tetracaine.2. Extracellular application of 20 /IM tetracaine reduced the increase in myoplasmic [Ca2"]. The effect on the underlying calcium release flux from the sarcoplasmic reticulum was to suppress the peak of the release while sparing the steady level attained at the end of 100 ms clamp depolarizations.3. While the peak of the release flux at corresponding voltages was reduced by 62 o after the addition of tetracaine, the rate of inactivation was the same when the pulses elicited release fluxes of similar amplitude.4. Higher concentrations of tetracaine, 0-2 mm, abolished the calcium signal in stretched fibres whereas in slack fibres this concentration left a non-inactivating calcium release flux.5. Lowering the extracellular pH antagonized the effect of the drug both on charge movements and on calcium signals. The permanently charged analogue tetracaine methobromide lacked effects on excitation-contraction coupling.6. These results imply that the two kinetic components of calcium release flux have very different tetracaine sensitivities. They are also consistent with an intracellular site of action of the drug at low concentration. Taken together they strongly suggest that the inactivating and non-inactivating components of calcium release correspond to different pathways: one that inactivates, is sensitive to tetracaine and is controlled by calcium, and another that does not inactivate, is much less sensitive to tetracaine and is directly controlled by voltage.

show abstract

Time course of calcium release and removal in skeletal muscle fibers

Cited by 153 publications

References 12 publications

Calcium inactivation of calcium release in frog cut muscle fibers that contain millimolar EGTA or Fura-2.

Calcium inactivation of calcium release in frog cut muscle fibers that contain millimolar EGTA or Fura-2.

Calcium release and its voltage dependence in frog cut muscle fibers equilibrated with 20 mM EGTA.

Differential effects of tetracaine on two kinetic components of calcium release in frog skeletal muscle fibres.

Contact Info

Product

Resources

About