Effects of diltiazem or verapamil on calcium uptake and release from chicken skeletal muscle sarcoplasmic reticulum

2005 ◽  
Vol 83 (11) ◽  
pp. 967-975 ◽  
Author(s):  
Mehrak Javadi Paydar ◽  
Abbas Pousti ◽  
Hasan Farsam ◽  
Massoud Amanlou ◽  
Shahram Ejtemaei Mehr ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Release Rate ◽  
Calcium Release ◽  
Inhibitory Effect ◽  
Channel Blockers ◽  
Uptake Inhibition ◽  
Drug Dependent ◽  
Chicken Skeletal Muscle

The purpose of this study was to determine the effects of 2 Ca2+ channel blockers, verapamil and diltiazem, on calcium loading (active Ca2+ uptake) and the following Ca2+ release induced by silver ion (Ag+) and Ca2+ from the membrane of heavy sarcoplasmic reticulum (SR) of chicken skeletal muscle. A fluorescent probe technique was employed to determine the calcium movement through the SR. Pretreatment of the medium with diltiazem and verapamil resulted in a significant decrease in the active Ca2+ uptake, with IC50 of about 290 µmol/L for verapamil and 260 µmol/L for diltiazem. Inhibition of Ca2+ uptake was not due to the development of a substantial drug-dependent leak of Ca2+ from the SR. It might, in part, have been mediated by a direct inhibitory effect of these drugs on the Ca2+ ATPase activity of the SR Ca2+ pump. We confirmed that Ca2+ channel blockers, administered after SR Ca2+ loading and before induction of Ca2+ release, caused a dose-dependent inhibition of both Ca2+- and Ag+-induced Ca2+ release rate. Moreover, if Ca2+ channel blockers were administered prior to SR Ca2+ loading, in spite of Ca2+ uptake inhibition the same reduction in Ca2+- and Ag+-induced Ca2+ release rate was seen. We showed that the inhibition of Ag+-induced Ca2+ release by L-channel blockers is more sensitive than Ca2+-induced Ca2+ release inhibition, so the IC50 for Ag+- and Ca2+-induced Ca2+ release was about 100 and 310 µmol/L for verapamil and 79 and 330 µmol/L for diltiazem, respectively. Our results support the evidence that Ca2+ channel blockers affect muscle microsome of chicken skeletal muscle by 2 independent mechanisms: first, reduction of Ca2+ uptake rate and Ca2+-ATPase activity inhibition, and second, inhibition of both Ag+- and Ca2+-induced Ca2+ release by Ca2+ release channels. These findings confirm the direct effect of Ca2+ channel blockers on calcium release channels. Our results suggest that even if the SR is incompletely preloaded with Ca2+ because of inhibition of Ca2+ uptake by verapamil and diltiazem, no impairment in Ca2+ release occurs. Key words: calcium, sarcoplasmic reticulum, diltiazem, verapamil, chicken, skeletal muscle.

scholarly journals The effects of thimerosal on calcium uptake and inositol 1,4,5-trisphosphate-induced calcium release in cerebellar microsomes

1993 ◽  
Vol 289 (3) ◽  
pp. 883-887 ◽  
Author(s):  
L G Sayers ◽  
G R Brown ◽  
R H Michell ◽  
F Michelangeli
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Calcium Uptake ◽  
Calcium Release ◽  
Hill Coefficient ◽  
Cysteine Residues ◽  
Experimental Conditions ◽  
Inositol 1,4,5 Trisphosphate ◽  
Insp3 Receptor

Thimerosal inhibits calcium uptake in skeletal muscle sarcoplasmic reticulum and rat cerebellar microsomes by inhibiting the Ca(2+)-ATPase. In the presence of 5 mM dithiothreitol (DTT), Ca2+ uptake and ATPase activity were not inhibited by thimerosal, indicating that thimerosal modifies cysteine residues of the Ca(2+)-ATPase. Low thimerosal concentrations (2 microM) sensitize the inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ channel, making it open at lower InsP3 concentrations. Higher concentrations of thimerosal, however, cause inhibition of InsP3-induced Ca2+ release. Both sensitization and inhibition of the InsP3 receptor by thimerosal can be prevented by DTT. The binding and metabolism of InsP3 by cerebellar microsomes is not affected by thimerosal. The amount of InsP3-induced Ca2+ release is co-operatively linked to the InsP3 concentration with a Hill coefficient of 2.0 +/- 0.3. This is decreased to 1.0 +/- 0.2 at inhibitory concentrations of thimerosal. Under our experimental conditions, we observed no dependence of quantal Ca2+ release on intraluminal Ca2+ concentration.

Calcium release rate in skinned skeletal muscle fibers measured with arsenazo III

1986 ◽  
Vol 250 (2) ◽  
pp. C245-C255 ◽  
Author(s):  
P. M. Best ◽  
M. Fill
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Release Rate ◽  
Calcium Release ◽  
Average Rate ◽  
Muscle Fibers ◽  
Rate Of Change ◽  
Arsenazo Iii ◽  
Correction Factors ◽  
Skeletal Muscle Fibers

Calcium ion release from the sarcoplasmic reticulum of single skinned (sarcolemma removed) skeletal muscle fibers was studied using the calcium-sensitive dye arsenazo III (Arz III). Isotropic absorption measurements were made differentially to reduce the effect of movement artifacts. The question of dye stoichiometry was addressed by measuring the absorption ratio at 600 and 660 nm at various times during the calcium transient. The results indicate that little change in the proportions of the various calcium-dye species occurs until at least 1 s into the release and, further, that the 1:2 calcium-dye complex is unlikely to be the dominant species present at early times. The relationship between dye concentration and the slope of the early absorption change was found to be linear for all levels of fiber loading. This suggests that the 1:1 rather than the 2:2 complex is the major species formed at early times in skinned fibers, although this conclusion is at odds with in vitro studies of Arz III in solution. Beer's law was used to convert the slope of the absorption transient measured over the first 125 ms of a release to the rate of change of the calcium-dye complex. The average rate at which the calcium-dye complex was formed was found to be 0.6 microM/ms. Two models are considered that allow calculation of a correction factor that is used to convert this value to the rate of calcium release from the sarcoplasmic reticulum. The magnitude of these correction factors was a function of the dye and intrinsic buffer concentrations as well as the stoichiometry of the calcium-dye reaction. After application of the correction factors, the average release rate in our fibers was calculated to range from 0.8 to 13.5 microM/ms.

Malignant hyperthermia with normal calcium-induced calcium release rate of sarcoplasmic reticulum in skeletal muscle

2002 ◽  
Vol 16 (1) ◽  
pp. 70-71
Author(s):  
Tetsuo Takaya ◽  
Kenji Ito ◽  
Mamoru Takiguchi ◽  
Yasuko Ichihara ◽  
Junji Sasaki ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Malignant Hyperthermia ◽  
Release Rate ◽  
Calcium Release ◽  
Calcium Induced Calcium Release ◽  
Normal Calcium

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.

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