Evidence for an inotropic positive action of cGMP during excitation–contraction coupling in frog sartorius muscle

1983 ◽  
Vol 61 (6) ◽  
pp. 590-594 ◽  
Author(s):  
L. Mancinelli ◽  
G. Fanò ◽  
L. Ferroni ◽  
T. Secca ◽  
B. M. Dolcini
Keyword(s):  
Calcium Release ◽  
Sartorius Muscle ◽  
Maximum Increase ◽  
General Hypothesis ◽  
Tension Development ◽  
Dantrolene Sodium ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius

Within the realm of the general hypothesis concerning the role of cGMP on intracellular calcium regulation in biological systems, we have investigated the action of cyclic nucleotides during excitation–contraction coupling in frog sartorius muscle. Our data show that several guanosine nucleotides (GTP, GDP, dibutyryl-cGMP) can increase the isometric twitch tension with a maximum increase of 40% in the muscles treated with cGMP. This increase is completely independent of external Ca2+ concentration. The use of dantrolene sodium (known to inhibit calcium release from sarcoplasmic reticulum) results in a decrease in the twitch tension with a contemporary decrease in the intracellular levels of cGMP; whereas, the addition of cGMP to the muscles treated with dantrolene antagonizes, at least partially, the effect of the drug on tension development. Finally, in chemically skinned muscles, cGMP induces a reversible contracture equal to approximately one-half of that evoked by 10−4 M Ca2+.

Association of increased pHi with calcium ion release in skeletal muscle

1978 ◽  
Vol 234 (3) ◽  
pp. C110-C114 ◽  
Author(s):  
R. J. Connett
Keyword(s):  
Skeletal Muscle ◽  
Calcium Ion ◽  
Calcium Release ◽  
Muscle Membrane ◽  
Sartorius Muscle ◽  
Ion Release ◽  
Extracellular Medium ◽  
Dantrolene Sodium ◽  
External Potassium ◽  
Frog Sartorius

The pH difference across the cell membrane of frog sartorius muscle cells was measured with the distribution of 5,5-dimethyl-2,4-oxazolidine-dione (DMO) as the marker. Depolarization of the muscles to values at or below the contraction threshold caused by elevating external potassium up to approximately 20 mM resulted in an internal alkalinization. The change was smaller with superthreshold depolarization (20--30 mM [K+]). The alkalinization was blocked by agents that block calcium release from the sarcoplasmic reticulum (procaine and dantrolene sodium). Other agents that cause calcium release (caffeine, theophylline, and quinine) were found to give alkalinization when tested at concentrations just below the contracture threshold. Increased acidification of the extracellular medium was associated with the internal alkalinization. The data were interpreted as indicating the presence of a calcium-stimulated H+ and/or OH- ion transport system in the muscle membrane.

scholarly journals Local movement in stimulated frog sartorius muscle.

1981 ◽  
Vol 78 (2) ◽  
pp. 151-170 ◽  
Author(s):  
G J Stienen ◽  
T Blangé
Keyword(s):  
Relative Length ◽  
Length Change ◽  
Sartorius Muscle ◽  
Tension Development ◽  
Frog Sartorius Muscle ◽  
Local Movement ◽  
Length Changes ◽  
Two Phases ◽  
Frog Sartorius ◽  
Relative Length Change

Local movement was recorded in tetanically contracting frog sartorius muscle to estimate the nonuniformity in the distribution of compliance in the muscle preparation and the compliance that resides in the attachments of the preparation to the measuring apparatus. The stimulated muscle was also subjected to rapid length changes, and the local movements and tension responses were recorded. The results indicate that during tension development at resting length the central region of the muscle shortens at the expense of the ends. After stimulation the "shoulder" in the tension, which divided the relaxation into a slow decline and a subsequent, rather exponential decay toward zero, was accompanied by an abrupt increase in local movement. We also examined the temperature sensitivity of the two phases of relaxation. The results are consistent with the view that the decrease in tension during relaxation depends on mechanical conditions. The local movement brought about by the imposed length changes indicates that the peak value of the relative length change of the uniformly acting part was approximately 20% less than the relative length change of the whole preparation. From these observations, corrections were obtained for the compliance data derived from the tension responses. These corrections allow a comparison with data in the literature obtained from single fiber preparations. The implications for the stiffness measured during the tension responses are discussed.

scholarly journals Quinine and Caffeine Effects on 45Ca Movements in Frog Sartorius Muscle

1967 ◽  
Vol 50 (8) ◽  
pp. 2109-2128 ◽  
Author(s):  
Allen Isaacson ◽  
Alexander Sandow
Keyword(s):  
Direct Action ◽  
Sartorius Muscle ◽  
High Concentration ◽  
Contraction Coupling ◽  
Twitch Potentiation ◽  
Ringer’S Solution ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius ◽  
45Ca Release ◽  
Uptake And Release

1 mM caffeine, which produces only twitch potentiation and not contracture in frog sartorius muscle, increases both the uptake and release of 45Ca in this muscle by about 50 %, thus acting like higher, contracture-producing concentrations but less intensely. Quinine increases the rate of release of 45Ca from frog sartorius but not from the Achilles tendon. The thresholds for the quinine effect on 45Ca release and contracture tension are about 0.1 and 0.5 mM, respectively, at pH 7.1. Quinine (2 mM) also doubles the uptake of 45Ca by normally polarized muscle. However, there are variable effects of quinine upon 45Ca uptake in potassium-depolarized muscle. Quinine (2 mM), increases the Ca, Na, and water content of muscle while decreasing the K content. Both caffeine (1 mM) and quinine (2 mM) act to release 45Ca from muscles that have been washed in Ringer's solution from which Ca was omitted and to which EDTA (5 mM) was added. These results, correlated with those of others, indicate that a basic effect of caffeine and quinine on muscle is to directly release activator Ca2+ from the sarcoplasmic reticulum in proportion to the drug concentration. The drugs may also enhance the depolarization-induced Ca release caused by extra K+ or an action potential. In respect to the myoplasmic Ca2+ released by direct action of the drugs, a relatively high concentration is required to activate even only threshold contracture, but a much lower concentration, added to that released during excitation-contraction coupling, is associated with the condition causing considerable twitch potentiation.

scholarly journals Action Potentials, Afterpotentials, and Excitation-Contraction Coupling in Frog Sartorius Fibers without Transverse Tubules

1969 ◽  
Vol 53 (3) ◽  
pp. 298-310 ◽  
Author(s):  
Peter W. Gage ◽  
Robert S. Eisenberg
Keyword(s):  
Membrane Potential ◽  
Short Duration ◽  
Action Potentials ◽  
Sartorius Muscle ◽  
Transverse Tubules ◽  
Excitation Contraction Coupling ◽  
Transverse Tubular System ◽  
Contraction Coupling ◽  
Tubular System ◽  
Frog Sartorius

In frog sartorius muscle fibers in which the transverse tubular system has been disrupted by treatment with glycerol, action potentials which are unaccompanied by twitches can be recorded. These action potentials appear to be the same as those recorded in normal fibers except that the early afterpotential usually consists of a small hyperpolarization of short duration. After a train of action potentials no late afterpotential is seen even when the membrane potential is changed from the resting level. In fibers without transverse tubules hyperpolarizing currents do not produce a creep in potential. The interruption of excitation-contraction coupling, the changes in the afterpotentials, and the disappearance of creep are all attributed to the lack of a transverse tubular system.

Role of the different calcium sources in the excitation–contraction coupling in crab muscle fibers

1987 ◽  
Vol 65 (4) ◽  
pp. 667-671 ◽  
Author(s):  
Y. Mounier ◽  
C. Goblet
Keyword(s):  
Calcium Release ◽  
Calcium Influx ◽  
Muscle Fibers ◽  
Mechanical Activity ◽  
Tension Development ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Extracellular Sodium ◽  
Tonic Tension

Excitation–contraction coupling in crab muscle fibers was studied in voltage-clamp conditions. Extracellular calcium is essential for the mechanical activity. Two calcium influxes induced by membrane depolarization contribute to tension development: one is the inward calcium current responsible for the phasic tension, the other is a calcium influx dependent on extracellular sodium and calcium concentrations and is responsible for the tonic tension. These calcium influxes are not sufficient to activate contractile proteins. Experiments with procaine and caffeine show that a calcium release from the sarcoplasmic reticulum is required.

scholarly journals Triadin Binding to the C-Terminal Luminal Loop of the Ryanodine Receptor is Important for Skeletal Muscle Excitation–Contraction Coupling

2007 ◽  
Vol 130 (4) ◽  
pp. 365-378 ◽  
Author(s):  
Sanjeewa A. Goonasekera ◽  
Nicole A. Beard ◽  
Linda Groom ◽  
Takashi Kimura ◽  
Alla D. Lyfenko ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Calcium Release ◽  
Striated Muscle ◽  
Single Channel ◽  
Triple Mutant ◽  
Double Mutation ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Functional Studies

Ca2+ release from intracellular stores is controlled by complex interactions between multiple proteins. Triadin is a transmembrane glycoprotein of the junctional sarcoplasmic reticulum of striated muscle that interacts with both calsequestrin and the type 1 ryanodine receptor (RyR1) to communicate changes in luminal Ca2+ to the release machinery. However, the potential impact of the triadin association with RyR1 in skeletal muscle excitation–contraction coupling remains elusive. Here we show that triadin binding to RyR1 is critically important for rapid Ca2+ release during excitation–contraction coupling. To assess the functional impact of the triadin-RyR1 interaction, we expressed RyR1 mutants in which one or more of three negatively charged residues (D4878, D4907, and E4908) in the terminal RyR1 intraluminal loop were mutated to alanines in RyR1-null (dyspedic) myotubes. Coimmunoprecipitation revealed that triadin, but not junctin, binding to RyR1 was abolished in the triple (D4878A/D4907A/E4908A) mutant and one of the double (D4907A/E4908A) mutants, partially reduced in the D4878A/D4907A double mutant, but not affected by either individual (D4878A, D4907A, E4908A) mutations or the D4878A/E4908A double mutation. Functional studies revealed that the rate of voltage- and ligand-gated SR Ca2+ release were reduced in proportion to the degree of interruption in triadin binding. Ryanodine binding, single channel recording, and calcium release experiments conducted on WT and triple mutant channels in the absence of triadin demonstrated that the luminal loop mutations do not directly alter RyR1 function. These findings demonstrate that junctin and triadin bind to different sites on RyR1 and that triadin plays an important role in ensuring rapid Ca2+ release during excitation–contraction coupling in skeletal muscle.

Constancy of Axial Spacings in Frog Sartorius Muscle during Contraction

Nature ◽  
1965 ◽  
Vol 206 (4991) ◽  
pp. 1358-1358 ◽  
Author(s):  
H. E. HUXLEY ◽  
W. BROWN ◽  
K. C. HOLMES
Keyword(s):  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius
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