scholarly journals The Influence of Hydrogen Ion Concentration on Calcium Binding and Release by Skeletal Muscle Sarcoplasmic Reticulum

1972 ◽  
Vol 59 (1) ◽  
pp. 22-32 ◽  
Author(s):  
Yoshiaki Nakamaru ◽  
Arnold Schwartz
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Ph Change ◽  
Release Process ◽  
Hydrogen Ion Concentration ◽  
Calcium Loading

Calcium release and binding produced by alterations in pH were investigated in isolated sarcoplasmic reticulum (SR) from skeletal muscle. When the pH was abruptly increased from 6.46 to 7.82, after calcium loading for 30 sec, 80–90 nanomoles (nmole) of calcium/mg protein were released. When the pH was abruptly decreased from 7.56 to 6.46, after calcium loading for 30 sec, 25–30 nmole of calcium/mg protein were rebound. The calcium release process was shown to be a function of pH change: 57 nmole of calcium were released per 1 pH unit change per mg protein. The amount of adenosine triphosphate (ATP) bound to the SR was not altered by the pH changes. The release phenomenon was not due to alteration of ATP concentration by the increased pH. Native actomyosin was combined with SR in order to study the effectiveness of calcium release from the SR by pH change in inducing super-precipitation of actomyosin. It was found that SR, in an amount high enough to inhibit superprecipitation at pH 6.5, did not prevent the process when the pH was suddenly increased to 7.3, indicating that the affinity of SR for calcium depends specifically on pH. These data suggest the possible participation of hydrogen ion concentration in excitation-contraction coupling.

Calsequestrin targeting to sarcoplasmic reticulum of skeletal muscle fibers

2006 ◽  
Vol 291 (2) ◽  
pp. C245-C253 ◽  
Author(s):  
Alessandra Nori ◽  
Giorgia Valle ◽  
Elena Bortoloso ◽  
Federica Turcato ◽  
Pompeo Volpe
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Structural Information ◽  
Muscle Fibers ◽  
Physiological Role ◽  
Homogeneous Distribution ◽  
Skeletal Muscle Fibers ◽  
Domain Iii

Calsequestrin (CS) is the low-affinity, high-capacity calcium binding protein segregated to the lumen of terminal cisternae (TC) of the sarcoplasmic reticulum (SR). The physiological role of CS in controlling calcium release from the SR depends on both its intrinsic properties and its localization. The mechanisms of CS targeting were investigated in skeletal muscle fibers and C2C12 myotubes, a model of SR differentiation, with four deletion mutants of epitope (hemagglutinin, HA)-tagged CS: CS-HAΔ24NH2, CS-HAΔ2D, CS-HAΔ3D, and CS-HAΔHT, a double mutant of the NH2 terminus and domain III. As judged by immunofluorescence of transfected skeletal muscle fibers, only the double CS-HA mutant showed a homogeneous distribution at the sarcomeric I band, i.e., it did not segregate to TC. As shown by subfractionation of microsomes derived from transfected skeletal muscles, CS-HAΔHT was largely associated to longitudinal SR whereas CS-HA was concentrated in TC. In C2C12 myotubes, as judged by immunofluorescence, not only CS-HAΔHT but also CS-HAΔ3D and CS-HAΔ2D were not sorted to developing SR. Condensation competence, a property referable to CS oligomerization, was monitored for the several CS-HA mutants in C2C12 myoblasts, and only CS-HAΔ3D was found able to condense. Together, the results indicate that 1) there are at least two targeting sequences at the NH2 terminus and domain III of CS, 2) SR-specific target and structural information is contained in these sequences, 3) heterologous interactions with junctional SR proteins are relevant for segregation, 4) homologous CS-CS interactions are involved in the overall targeting process, and 5) different targeting mechanisms prevail depending on the stage of SR differentiation.

scholarly journals Lactic acid in mammalian cardiac muscle.— Part III. changes in hydrogen-ion concentration. (Preliminary note.)

1925 ◽  
Vol 99 (694) ◽  
pp. 26-27 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Lactic Acid ◽  
Glass Electrode ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Accurate Estimation ◽  
Rigor Mortis ◽  
Preliminary Note ◽  
Hydrogen Ion Concentration ◽  
Electrode Method

Experiments have been made to determine (1) the hydrogen-ion concentra­tions of cardiac and skeletal muscle minced in the cold ( a ) under normal con­ditions, ( b )after stimulation to fatigue, and ( c ) in rigor mortis, and (2) the change of hydrogen-ion concentration following the addition of known amounts of lactic acid. The measurements were made by means of the glass electrode method (Kerridge (1)). The results given are quantitatively only preliminary in character, pending (i) the repetition of the experiments on a larger number of animals, and (ii) the more accurate estimation of corrections due to dilution with saline, &c.

scholarly journals Calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum in skeletal muscle fibers.

1991 ◽  
Vol 97 (3) ◽  
pp. 437-471 ◽  
Author(s):  
B J Simon ◽  
M G Klein ◽  
M F Schneider
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Calcium Release ◽  
Muscle Fibers ◽  
Calcium Transients ◽  
Calcium Dependence ◽  
Fura 2 ◽  
Test Pulse ◽  
Calcium Dependent

The steady-state calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum was studied in voltage-clamped, cut segments of frog skeletal muscle fibers containing two calcium indicators, fura-2 and anti-pyrylazo III (AP III). Fura-2 fluorescence was used to monitor resting calcium and relatively small calcium transients during small depolarizations. AP III absorbance signals were used to monitor larger calcium transients during larger depolarizations. The rate of release (Rrel) of calcium from the sarcoplasmic reticulum was calculated from the calcium transients. The equilibrium calcium dependence of inactivation of calcium release was determined using 200-ms prepulses of various amplitudes to elevate [Ca2+] to various steady levels. Each prepulse was followed by a constant test pulse. The suppression of peak Rrel during the test pulse provided a measure of the extent of inactivation of release at the end of the prepulse. The [Ca2+] dependence of inactivation indicated that binding of more than one calcium ion was required to inactivate each release channel. Half-maximal inactivation was produced at a [Ca2+] of approximately 0.3 microM. Variation of the prepulse duration and amplitude showed that the suppression of peak release was consistent with calcium-dependent inactivation of calcium release but not with calcium depletion. The same calcium dependence of inactivation was obtained using different amplitude test pulses to determine the degree of inactivation. Prepulses that produced near maximal inactivation of release during the following test pulse produced no suppression of intramembrane charge movement during the test pulse, indicating that inactivation occurred at a step beyond the voltage sensor for calcium release. Three alternative set of properties that were assumed for the rapidly equilibrating calcium-binding sites intrinsic to the fibers gave somewhat different Rrel records, but gave very similar calcium dependence of inactivation. Thus, equilibrium inactivation of calcium release appears to be produced by rather modest increases in [Ca2+] above the resting level and in a steeply calcium-dependent manner. However, the inactivation develops relatively slowly even during marked elevation of [Ca2+], indicating that a calcium-independent transition appears to occur after the initial calcium-binding step.

fatty acids modulate calcium-induced calcium release from skeletal muscle heavy sarcoplasmic reticulum fractions: implications for mallignant hyperthermia

1990 ◽  
Vol 68 (10) ◽  
pp. 1195-1201 ◽  
Author(s):  
Jeffrey E. Fletcher ◽  
Linda Tripolitis ◽  
Kirsten Erwin ◽  
Susan Hanson ◽  
Henry Rosenberg ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acids ◽  
Fatty Acid ◽  
Sarcoplasmic Reticulum ◽  
Malignant Hyperthermia ◽  
Calcium Release ◽  
Unsaturated Fatty Acids ◽  
Malignant Hyperthermia Susceptibility ◽  
Muscle Rigidity ◽  
Release Process

Based on studies in swine, the malignant hyperthermia syndrome has been postulated to result from an enhanced sensitivity (low threshold) of the Ca2+-induced Ca2+-release process. However, fatty acid production is elevated in homogenates of skeletal muscle from pigs and humans susceptible to malignant hyperthermia. In the present study, we demonstrate that the threshold of Ca2+-induced Ca2+ release is normal in susceptible humans and in susceptible swine depleted of triglycerides. Exogenously added unsaturated fatty acids decreased the threshold of Ca2+-induced Ca2+ release to a much greater extent in porcine and equine muscle than in human muscle. When triglyceride and free fatty acid values were reduced to about 40 and 60%, respectively, of control values, malignant hyperthermia-susceptible swine did not exhibit muscle rigidity when challenged in vivo with halothane and succinylcholine and the threshold of the Ca2+-induced Ca2+-release process in heavy sarcoplasmic reticulum fractions was normal. Despite the reduced triglyceride and fatty acid levels, these swine had a positive in vitro contracture test for malignant hyperthermia. A low Ca2+-induced Ca2+-release threshold is not essential for malignant hyperthermia susceptibility, but appears to be the result of excessive free fatty acids produced during organelle isolation.Key words: calcium release, fatty acids, malignant hyperthermia, triglycerides.

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