Effects of repetitive activity, ruthenium red, and elevated extracellular calcium on frog skeletal muscle: implications for t-tubule conduction

1987 ◽  
Vol 65 (4) ◽  
pp. 691-696 ◽  
Author(s):  
John N. Howell ◽  
Hans Oetliker
Keyword(s):  
Calcium Concentration ◽  
Ruthenium Red ◽  
Extracellular Calcium ◽  
Frog Skeletal Muscle ◽  
Contraction Coupling ◽  
Force Development ◽  
High Calcium ◽  
Conduction Failure ◽  
New Evidence ◽  
T System

In this report we review evidence that indicates that experimental elevation of t-tubular calcium can lead to failure of action potential propagation within the t system and we present some new evidence suggesting that t-tubular calcium concentration may rise during repetitive activity. The evidence for t-tubular conduction failure consists of comparisons of the effects of high calcium and of ruthenium red on excitation and excitation–contraction coupling as well as morphological observations of wavy myofibrils in the axial core of fibers contracting tetanically in solutions containing elevated calcium concentrations. Evidence for elevation of t-tubular calcium concentration during repetitive activity comes from the following. During twitches, the early, large birefringence signal and force development arc delayed in onset if the extracellular calcium and (or) potassium concentrations are above normal or if the fiber has been stimulated tetanically just prior to the test twitch. The delays that occur in twitches following tetanic contractions are attenuated when the extracellular and, therefore, the t-tubular calcium concentration is buffered with citrate.

Requirement for transmembrane sodium flux in maintenance of cytosolic calcium levels in rat Sertoli cells

1993 ◽  
Vol 264 (6) ◽  
pp. E863-E867 ◽  
Author(s):  
E. Gorczynska ◽  
D. J. Handelsman
Keyword(s):  
Sertoli Cells ◽  
Calcium Concentration ◽  
Cytosolic Calcium ◽  
Ruthenium Red ◽  
Extracellular Calcium ◽  
Isolated Cells ◽  
Acetoxymethyl Ester ◽  
Calcium Fluxes ◽  
Calcium Exchange ◽  
Extracellular Sodium

The prompt rise in cytosolic calcium induced by follicle-stimulating hormone (FSH) in rat Sertoli cells suggests a role for calcium in FSH signal transduction. To evaluate the requirement for sodium in transmembrane calcium fluxes in Sertoli cells, we measured intracellular calcium concentration under sodium-free conditions and during stimulation by monensin and veratridine, used to elevate cytosolic sodium. Cytosolic calcium levels were measured by dual-wavelength spectrofluorimetry using freshly isolated cells loaded with fura-2 acetoxymethyl ester. Whereas, removal of extracellular sodium lowered cytosolic calcium in unstimulated cells from 89 +/- 4 to 75 +/- 8 nM, treatment with monensin and veratridine increased cytosolic calcium to 142 +/- 19 and 126 +/- 13 nM, respectively. Without extracellular calcium, monensin still produced 47% of the rise in cytosolic calcium observed in the presence of extracellular calcium, indicating approximately equal contributions of calcium from intracellular and extracellular sources. Blockade of voltage-sensitive or/and voltage-insensitive calcium channels by verapamil and ruthenium red was unable to completely prevent the monensin-induced elevation of cytosolic calcium. In addition tetrodotoxin failed to block the FSH-induced rise in cytosolic calcium. These observations, together with the considerable reduction in monensin-induced rise in cytosolic calcium under extracellular sodium-free condition, support the hypothesis that sodium-calcium exchange rather than the specific calcium or sodium channels regulate basal and monensin-induced transmembrane sodium and calcium fluxes in Sertoli cells.

scholarly journals The T-SR junction in contracting single skeletal muscle fibers.

1982 ◽  
Vol 79 (1) ◽  
pp. 1-19 ◽  
Author(s):  
B R Eisenberg ◽  
R S Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Amorphous Material ◽  
Frog Skeletal Muscle ◽  
Contraction Coupling ◽  
Single Fibers ◽  
Line Parallel ◽  
Rich Solution ◽  
Electron Lucent ◽  
T System

The junction between the T system and sarcoplasmic reticulum (SR) of frog skeletal muscle was examined in resting and contracting muscles. Pillars, defined as pairs of electron-opaque lines bounding an electron-lucent interior, were seen spanning the gap between T membrane and SR. Feet, defined previously in images of heavily stained preparations, appear with electron-opaque interiors and as such are distinct from the pillars studied here. Amorphous material was often present in the gap between T membrane and SR. Sometimes the amorphous material appeared as a thin line parallel to the membranes; sometimes it seemed loosely organized at the sites where feet have been reported. Resting single fibers contained 39 +/- 14.3 (mean +/- SD; n = 9 fibers) pillars/micrometer2 of tubule membrane. Single fibers, activated by a potassium-rich solution at 4 degrees C, contained 66 +/- 12.9 pillars/micrometer2 (n = 8) but fibers contracting in response to 2 mM caffeine contained 33 +/- 8.6/micrometer2 (n = 5). Pillar formation occurs when fibers are activated electrically, but not when calcium is released directly from the SR; and so we postulate that pillar formation is a step in excitation-contraction coupling.

Inhibition of tetanus tension by elevated extracellular calcium concentration

1981 ◽  
Vol 240 (5) ◽  
pp. C193-C200 ◽  
Author(s):  
J. N. Howell ◽  
K. W. Snowdowne
Keyword(s):  
Skeletal Muscle ◽  
Action Potentials ◽  
Calcium Concentration ◽  
Extracellular Calcium ◽  
Frog Skeletal Muscle ◽  
Transverse Tubular System ◽  
Microelectrode Recordings ◽  
Tubular System ◽  
Osmotic Effects ◽  
Reversible Reduction

Extracellular [Ca2+] in the range of 5-20 mM produces a concentration-dependent reversible reduction in tetanus tension in single frog skeletal muscle fibers. Both peak tension and ability to sustain tension during tetanus is reduced. The effect is unrelated to osmotic effects and independent of stimulation frequency in the range 100-200 Hz. The effect occurs both at 8 and 24 degrees C. Tetanus tension is most strongly inhibited by elevated extracellular [Ca2+] at short muscle lengths, but the effect can be seen at all lengths. Microelectrode recordings during tetanus indicate that action potentials remain undiminished in amplitude and duration throughout the tetanus. The evidence suggests that the inhibition results from a failure of action potentials propagation within the transverse tubular system.

scholarly journals CaSR-Mediated hBMSCs Activity Modulation: Additional Coupling Mechanism in Bone Remodeling Compartment

2020 ◽  
Vol 22 (1) ◽  
pp. 325
Author(s):  
Hyunji Cho ◽  
Jisoo Lee ◽  
Seoyoung Jang ◽  
Jungsun Lee ◽  
Tong In Oh ◽  
...  
Keyword(s):  
Bone Remodeling ◽  
Calcium Concentration ◽  
Apoptotic Cell ◽  
Extracellular Calcium ◽  
Coupling Mechanism ◽  
Differentiation Potential ◽  
High Calcium ◽  
Significant Difference ◽  
High Calcium Concentration

Near the bone remodeling compartments (BRC), extracellular calcium concentration (Ca2+o) is locally elevated and bone marrow stromal cells (BMSCs) close to the BRC can be exposed to high calcium concentration. The calcium-sensing receptor (CaSR) is known to play a key role in maintaining extracellular calcium homeostasis by sensing fluctuations in the levels of extracellular calcium (Ca2+o). When human BMSCs (hBMSCs) were exposed to various calcium concentrations (1.8, 3, 5, 10, 30 mM), moderate-high extracellular calcium concentrations (3–5 mM) stimulated proliferation, while a high calcium concentration (30 mM) inhibited the proliferation. Exposure to various calcium concentrations did not induce significant differences in the apoptotic cell fraction. Evaluation of multi-lineage differentiation potential showed no significant difference among various calcium concentration groups, except for the high calcium concentration (30 mM) treated group, which resulted in increased calcification after in vitro osteogenic differentiation. Treatment of NPS2143, a CaSR inhibitor, abolished the stimulatory effect on hBMSCs proliferation and migration indicating that CaSR is involved. These results suggest that the calcium concentration gradient near the BRC may play an important role in bone remodeling by acting as an osteoblast–osteoclast coupling mechanism through CaSR.

scholarly journals Effect of Ruthenium Red on Excitation-Contraction Coupling in Frog Skeletal Muscle

1980 ◽  
Vol 30 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Toshiko SUZUKI ◽  
Kazuo OBARA ◽  
Torao NAGAI
Keyword(s):  
Skeletal Muscle ◽  
Ruthenium Red ◽  
Frog Skeletal Muscle ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling
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