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

Sarcoplasmic reticulum (SR) Ca release was studied at 13-16 degrees C in cut fibers (sarcomere length, 3.4-3.9 microns) 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 delta pH signal measured with phenol red by -beta/2. The value of beta, 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 microM in the action-potential experiments and 2,544 microM 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 approximately 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 approximately 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 7,000 and increase the value of spatially averaged myoplasmic free [Ca] by only 0.2 nM.

[1]  E. Ríos,et al.  Time course of calcium release and removal in skeletal muscle fibers. , 1984, Biophysical journal.

[2]  B. Hille,et al.  An improved vaseline gap voltage clamp for skeletal muscle fibers , 1976, The Journal of general physiology.

[3]  Y. Ogawa,et al.  Re-examination of the apparent binding constant of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid with calcium around neutral pH. , 1980, Journal of biochemistry.

[4]  W. Chandler,et al.  OPTICAL INDICATIONS OF EXCITATION-CONTRACTION COUPLING IN STRIATED MUSCLE , 1978 .

[5]  N. Sizto,et al.  Calcium signals recorded from cut frog twitch fibers containing tetramethylmurexide , 1987, The Journal of general physiology.

[6]  M. F. Schneider,et al.  Calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum in skeletal muscle fibers , 1991, The Journal of general physiology.

[7]  S. Baylor,et al.  Use of fura red as an intracellular calcium indicator in frog skeletal muscle fibers. , 1993, Biophysical journal.

[8]  L. Blatter,et al.  Simultaneous measurement of Ca2+ in muscle with Ca electrodes and aequorin. Diffusible cytoplasmic constituent reduces Ca(2+)-independent luminescence of aequorin , 1991, The Journal of general physiology.

[9]  M. F. Schneider,et al.  Inactivation of calcium release from the sarcoplasmic reticulum in frog skeletal muscle. , 1988, The Journal of physiology.

[10]  K. Campbell,et al.  Structural evidence for direct interaction between the molecular components of the transverse tubule/sarcoplasmic reticulum junction in skeletal muscle , 1988, The Journal of cell biology.

[11]  W. Chandler,et al.  Calcium signals recorded from two new purpurate indicators inside frog cut twitch fibers , 1989, The Journal of general physiology.

[12]  W. Chandler,et al.  Calcium inactivation of calcium release in frog cut muscle fibers that contain millimolar EGTA or Fura-2 , 1995, The Journal of general physiology.

[13]  S. Baylor,et al.  Valinomycin and excitation‐contraction coupling in skeletal muscle fibres of the frog. , 1992, The Journal of physiology.

[14]  M. W. Marshall,et al.  Optical measurements of intracellular pH and magnesium in frog skeletal muscle fibres , 1982, The Journal of physiology.

[15]  E. Stefani,et al.  Effects of extracellular calcium on calcium movements of excitation‐contraction coupling in frog skeletal muscle fibres. , 1988, The Journal of physiology.

[16]  S. Baylor,et al.  Myoplasmic calcium transients in intact frog skeletal muscle fibers monitored with the fluorescent indicator furaptra , 1991, The Journal of general physiology.

[17]  H. Huxley,et al.  FILAMENT LENGTHS IN STRIATED MUSCLE , 1963, The Journal of cell biology.

[18]  S. Baylor,et al.  Myoplasmic binding of fura-2 investigated by steady-state fluorescence and absorbance measurements. , 1988, Biophysical journal.

[19]  E. Ríos,et al.  A general procedure for determining the rate of calcium release from the sarcoplasmic reticulum in skeletal muscle fibers. , 1987, Biophysical journal.

[20]  S. Baylor,et al.  Fura‐2 calcium transients in frog skeletal muscle fibres. , 1988, The Journal of physiology.

[21]  W. Chandler,et al.  Effect of fura-2 on action potential-stimulated calcium release in cut twitch fibers from frog muscle , 1993, The Journal of general physiology.

[22]  N. Sizto,et al.  Intracellular diffusion in the presence of mobile buffers. Application to proton movement in muscle. , 1990, Biophysical journal.

[23]  S. Baylor,et al.  Changes in phenol red absorbance in response to electrical stimulation of frog skeletal muscle fibers , 1990, The Journal of general physiology.

[24]  W J Crozier,et al.  The Journal of General Physiology , 1919, Botanical Gazette.

[25]  R. Vaughan-Jones,et al.  Continuous direct measurement of intracellular chloride and pH in frog skeletal muscle , 1977, The Journal of physiology.

[26]  J. Lisman,et al.  The initiation of excitation and light adaptation in Limulus ventral photoreceptors , 1979, Vision Research.

[27]  D. Maughan,et al.  On the composition of the cytosol of relaxed skeletal muscle of the frog. , 1988, The American journal of physiology.

[28]  L. Rosenhead Conduction of Heat in Solids , 1947, Nature.

[29]  R. Tsien,et al.  A new generation of Ca2+ indicators with greatly improved fluorescence properties. , 1985, The Journal of biological chemistry.

[30]  L. Csernoch,et al.  Voltage-gated and calcium-gated calcium release during depolarization of skeletal muscle fibers. , 1991, Biophysical journal.

[31]  S. Baylor,et al.  Resting myoplasmic free calcium in frog skeletal muscle fibers estimated with fluo-3. , 1993, Biophysical journal.

[32]  M. F. Schneider,et al.  Depletion of calcium from the sarcoplasmic reticulum during calcium release in frog skeletal muscle. , 1987, The Journal of physiology.

[33]  S. Baylor,et al.  Absorbance signals from resting frog skeletal muscle fibers injected with the pH indicator dye, phenol red , 1990, The Journal of general physiology.

[34]  N. Sizto,et al.  Intrinsic optical and passive electrical properties of cut frog twitch fibers , 1987, The Journal of general physiology.

[35]  N. Curtin Buffer power and intracellular pH of frog sartorius muscle. , 1986, Biophysical journal.

[36]  R. Llinás,et al.  Compartmentalization of the submembrane calcium activity during calcium influx and its significance in transmitter release. , 1985, Biophysical journal.

[37]  N. Sizto,et al.  Simultaneous monitoring of changes in magnesium and calcium concentrations in frog cut twitch fibers containing antipyrylazo III , 1989, The Journal of general physiology.

[38]  J. Johnson,et al.  Parvalbumin content and Ca2+ and Mg2+ dissociation rates correlated with changes in relaxation rate of frog muscle fibres. , 1991, The Journal of physiology.

[39]  M. Klein,et al.  Effects of caffeine on calcium release from the sarcoplasmic reticulum in frog skeletal muscle fibres. , 1990, The Journal of physiology.

[40]  E. Ríos,et al.  Voltage Sensors and Calcium Channels of Excitation-Contraction Coupling , 1988 .

[41]  Lee D. Peachey,et al.  THE SARCOPLASMIC RETICULUM AND TRANSVERSE TUBULES OF THE FROG'S SARTORIUS , 1965, The Journal of cell biology.

[42]  K. Campbell,et al.  Ryanodine receptor of skeletal muscle is a gap junction-type channel. , 1988, Science.

[43]  M. Stern,et al.  Buffering of calcium in the vicinity of a channel pore. , 1992, Cell calcium.

[44]  S. Baylor,et al.  Excitation-contraction coupling in intact frog skeletal muscle fibers injected with mmolar concentrations of fura-2. , 1992, Biophysical journal.

[45]  E. Ríos,et al.  Measurement and modification of free calcium transients in frog skeletal muscle fibres by a metallochromic indicator dye. , 1983, The Journal of physiology.

[46]  M. Shimizu [Electrolyte solutions]. , 2019, [Kango] Japanese journal of nursing.

[47]  R. Young,et al.  Proton permeability of sarcoplasmic reticulum vesicles. , 1980, The Journal of biological chemistry.

[48]  R. Miledi,et al.  Effects of membrane polarization on sarcoplasmic calcium release in skeletal muscle , 1981, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[49]  G. Lamb,et al.  Effect of myoplasmic pH on excitation‐contraction coupling in skeletal muscle fibres of the toad. , 1992, The Journal of physiology.

[50]  R L Berger,et al.  A stopped-flow investigation of calcium ion binding by ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid. , 1984, Analytical biochemistry.

[51]  M. W. Marshall,et al.  Use of metallochromic dyes to measure changes in myoplasmic calcium during activity in frog skeletal muscle fibres , 1982, The Journal of physiology.

[52]  Fred J. Sigworth,et al.  Fitting and Statistical Analysis of Single-Channel Records , 1983 .

[53]  M. Kushmerick,et al.  Ionic Mobility in Muscle Cells , 1969, Science.

[54]  C. Franzini-armstrong Membrane particles and transmission at the triad. , 1975, Federation proceedings.

[55]  David Colquhoun,et al.  Lectures on biostatistics , 1972 .

[56]  S. Baylor,et al.  Perturbation of sarcoplasmic reticulum calcium release and phenol red absorbance transients by large concentrations of fura-2 injected into frog skeletal muscle fibers , 1990, The Journal of general physiology.

[57]  M. W. Marshall,et al.  Sarcoplasmic reticulum calcium release in frog skeletal muscle fibres estimated from Arsenazo III calcium transients. , 1983, The Journal of physiology.

[58]  N. Sizto,et al.  Calcium signals recorded from cut frog twitch fibers containing antipyrylazo III , 1987, The Journal of general physiology.

[59]  R Y Tsien,et al.  Ca2+ binding kinetics of fura-2 and azo-1 from temperature-jump relaxation measurements. , 1988, Biophysical journal.

[60]  N. Sizto,et al.  Comparison of arsenazo III optical signals in intact and cut frog twitch fibers , 1987, The Journal of general physiology.

[61]  J. Vergara,et al.  Arsenazo III and antipyrylazo III calcium transients in single skeletal muscle fibers , 1982, The Journal of general physiology.

[62]  M. F. Schneider,et al.  Simultaneous recording of calcium transients in skeletal muscle using high- and low-affinity calcium indicators. , 1988, Biophysical journal.

[63]  E. Neher,et al.  Concentration profiles of intracellular calcium in the presence of a diffusible chelator. , 1986 .

[64]  R. Putnam,et al.  The intracellular pH of frog skeletal muscle: its regulation in isotonic solutions. , 1983, The Journal of physiology.