An appraisal of the evidence for a sarcoplasmic reticulum membrane potential and its relation to calcium release in skeletal muscle

1982 ◽  
Vol 3 (3) ◽  
pp. 247-272 ◽  
Author(s):  
Hans Oetliker
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Sarcoplasmic Reticulum Membrane

Caffeine treatment inhibits drug-induced calcium release from sarcoplasmic reticulum and caffeine contracture but not tetanus in frog skeletal muscle

1989 ◽  
Vol 67 (8) ◽  
pp. 890-895 ◽  
Author(s):  
Makoto Koshita ◽  
Toshiharu Oba
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Electrical Stimulus ◽  
Final Concentration ◽  
Heavy Fraction ◽  
Frog Skeletal Muscle ◽  
Drug Induced ◽  
Physiological Signal ◽  
Caffeine Contracture

Effects of pretreatment with caffeine on Ca2+ release induced by caffeine, thymol, quercetin, or p-chloromercuriphenylsulfonic acid (pCMPS) from the heavy fraction of sarcoplasmic reticulum (SR) were studied and compared with those effects on caffeine contracture and tetanus tension in single fibers of frog skeletal muscle. Caffeine (1–5 mM) did induce transient Ca2+ release from SR vesicles, but subsequent further addition of caffeine (10 mM, final concentration) induced little Ca2+ release. Ca2+ release induced by thymol, quercetin, or pCMPS was also inhibited by pretreatment with caffeine. In single muscle fibers, pretreatment with caffeine (1–5 mM) partially reduced the contracture induced by 10 mM caffeine. However, tetanus tension was almost maximally induced by electrical stimulus in caffeine-treated fibers. These results indicate that SR, which becomes less sensitive to caffeine, thymol, quercetin, or pCMPS by pretreatment with caffeine, can still respond to a physiological signal transmitted from transverse tubules.Key words: Ca2+ release, sarcoplasmic reticulum, caffeine, tetanus, skeletal muscle.

Ca(2+)- and pH-dependent halothane stimulation of Ca2+ release in sarcoplasmic reticulum from frog muscle

1996 ◽  
Vol 271 (2) ◽  
pp. C540-C546 ◽  
Author(s):  
M. Beltran ◽  
R. Bull ◽  
P. Donoso ◽  
C. Hidalgo
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Release Kinetics ◽  
Frog Muscle ◽  
Time Range ◽  
Frog Skeletal Muscle ◽  
Open Probability ◽  
Filtration System ◽  
Stimulation Of

The effect of halothane on calcium release kinetics was studied in triad-enriched sarcoplasmic reticulum vesicles from frog skeletal muscle. Release from vesicles passively equilibrated with 3 mM 45CaCl2 was measured in the millisecond time range by use of a fast-filtration system. Halothane (400 microM) increased release rate constants at pH 7.1 and 7.4 as a function of extravesicular pCa. In contrast, halothane at pH 6.8 produced the same stimulation of release from pCa 7.0 to 3.0; no release took place in these conditions in the absence of halothane. Halothane shifted the calcium activation curve at pH 7.1, but not at pH 7.4, to the left and increased channel open probability at pH 7.1 in the cis pCa range of 7.0 to 5.0. These results indicate that cytosolic pCa and pH modulate the stimulatory effects of halothane on calcium release. Furthermore, halothane stimulated release in frog skeletal muscle at low pH and resting calcium concentration, indicating that in frog muscle halothane can override the closing of the release channels produced by these conditions, as it does in malignant hyperthermia-susceptible porcine muscle.

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