Effects of uridine triphosphate on skinned skeletal muscle fibers of the rat

1995 ◽  
Vol 73 (10) ◽  
pp. 1451-1457 ◽  
Author(s):  
G. Suarez-Kurtz ◽  
C. G. Ponte ◽  
M.-P. Catinot ◽  
Y. Mounier ◽  
R. Vianna-Jorge
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Muscle Fibers ◽  
Ruthenium Red ◽  
Uridine Triphosphate ◽  
Skinned Muscle ◽  
Brij 58 ◽  
Longus Muscle ◽  
Nonionic Detergent ◽  
Skinned Muscle Fiber ◽  
Sarcoplasmic Reticulum Calcium

Chemically skinned muscle fibers from rat extensor digitorum longus muscle were used to study the effects of uridine triphosphate (UTP) on Ca2+ uptake and release by the sarcoplasmic reticulum (SR) and on Ca2+-activated tensions. Total replacement (2.5 mM) of adenosine triphosphate (ATP) with UTP (i) increased submaximal Ca2+-induced tension (pCa 6.2–5.8) but diminished Po, the maximum tension elicited by pCa 4.2, by ca. 15%; (ii) markedly reduced Ca2+ uptake by the SR (evaluated by caffeine-elicited tension); and (iii) induced tension in Ca2+-loaded fibers. The UTP-induced tension averaged 55% of Po and its rates of development and decay were considerably slower than those of caffeine-evoked tension. The UTP-induced tension (i) depended on the Ca2+-loading conditions; (ii) was reversibiy blocked by brief (15 s) exposures of Ca2+-loaded fibers to 5 mM EGTA or by pretreatment with caffeine; (iii) was abolished by functional disruption of the SR with the nonionic detergent Brij-58; and (iv) persisted after blockade of the SR Ca2+ release channels with ruthenium red. Exposure of Ca2+-loaded fibers to UTP depressed the tension elicited subsequently by caffeine, and enhanced the rate of depletion of caffeine-sensitive Ca2+ stores during soaking in relaxing solutions containing 5 mM EGTA. The UTP-induced tension is attributed to increased release of Ca2+ from the SR, via a ruthenium red insensitive pathway(s), combined with reduced Ca2+ uptake by the SR and increased Ca2+ affinity of the contractile proteins.Key words: skinned muscle fiber, UTP-induced tension, tension–pCa relationship, sarcoplasmic reticulum, calcium transport.

Functional effects of uridine triphosphate on human skinned skeletal muscle fibers

1998 ◽  
Vol 76 (2) ◽  
pp. 110-117 ◽  
Author(s):  
R Vianna-Jorge ◽  
C F Oliveira ◽  
Y Mounier ◽  
G Suarez-Kurtz
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Muscle Fibers ◽  
Fiber Types ◽  
Release Channel ◽  
Uridine Triphosphate ◽  
Skinned Muscle ◽  
Skeletal Muscle Fibers ◽  
Slow Type ◽  
Relationship Of

Chemically skinned human skeletal muscle fibers were used to study the effects of uridine triphosphate (UTP) on the tension-pCa relationship and on Ca2+ uptake and release by the sarcoplasmic reticulum (SR). Total replacement (2.5 mM) of adenosine triphosphate (ATP) with UTP (i) displaced the tension-pCa relationship to the left along the abcissae and increased maximum Ca2+-activated tension, both effects being larger in slow- than in fast-type fibers; (ii) markedly reduced Ca2+ uptake by the SR (evaluated by the caffeine-evoked tension) in both fiber types; (iii) had no effect on the rate of depletion of caffeine-sensitive Ca2+ stores during soaking in relaxing solutions; (iv) induced tension in slow- but not in fast-type fibers. The effects on the SR functional properties are consistent with the notion that UTP is a poor substitute for ATP as a substrate for the Ca ATPase pump and as an agonist of the ryanodine-sensitive Ca2+-release channel. The UTP-induced tension in human slow-type fibers is attributed to effect(s) of the nucleotide on the tension-pCa relationship of the contractile machinery. The present data reveal important differences between the effects of UTP on human versus rat muscle fibers.Key words: skinned muscle fiber, UTP-induced tension, tension-pCa relationship, sarcoplasmic reticulum, calcium transport.

scholarly journals Calcium-gated calcium channels in sarcoplasmic reticulum of rabbit skinned skeletal muscle fibers.

1986 ◽  
Vol 87 (2) ◽  
pp. 289-303 ◽  
Author(s):  
P Volpe ◽  
G Salviati ◽  
A Chu
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Ruthenium Red ◽  
Scattering Method ◽  
Tension Development ◽  
Maximal Force ◽  
Skeletal Muscle Fibers ◽  
Ca2 Channels

The action of ruthenium red (RR) on Ca2+ loading by and Ca2+ release from the sarcoplasmic reticulum (SR) of chemically skinned skeletal muscle fibers of the rabbit was investigated. Ca2+ loading, in the presence of the precipitating anion pyrophosphate, was monitored by a light-scattering method. Ca2+ release was indirectly measured by following tension development evoked by caffeine. Stimulation of the Ca2+ loading rate by 5 microM RR was dependent on free Ca2+, being maximal at pCa 5.56. Isometric force development induced by 5 mM caffeine was reversibly antagonized by RR. IC50 for the rate of tension rise was 0.5 microM; that for the extent of tension was 4 microM. RR slightly shifted the steady state isometric force/pCa curve toward lower pCa values. At 5 microM RR, the pCa required for half-maximal force was 0.2 log units lower than that of the control, and maximal force was depressed by approximately 16%. These results suggest that RR inhibited Ca2+ release from the SR and stimulated Ca2+ loading into the SR by closing Ca2+-gated Ca2+ channels. Previous studies on isolated SR have indicated the selective presence of such channels in junctional terminal cisternae.

Differential Effects of Sevoflurane, Isoflurane, and Halothane on Ca (2+) Release from the Sarcoplasmic Reticulum of Skeletal Muscle 

1999 ◽  
Vol 91 (1) ◽  
pp. 179-186 ◽  
Author(s):  
Gudrun Kunst ◽  
Bernhard M. Graf ◽  
Rupert Schreiner ◽  
Eike Martin ◽  
Rainer H. A. Fink
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Muscle Fibers ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Maximal Force ◽  
Skinned Muscle ◽  
Skeletal Muscle Fibers ◽  
Force Relation ◽  
The Individual

Background Although malignant hyperthermia after application of sevoflurane has been reported, little is known about its action on intracellular calcium homeostasis of skeletal muscle. The authors compared the effect of sevoflurane with that of isoflurane and halothane on Ca2+ release of mammalian sarcoplasmic reticulum and applied a novel method to quantify Ca2+ turnover in permeabilized skeletal muscle fibers. Methods Liquid sevoflurane, isoflurane, and halothane at 0.6 mM, 3.5 mM, and 7.6 mm were diluted either in weakly calcium buffered solutions with no added Ca2+ (to monitor Ca2+ release) or in strongly Ca2+ buffered solutions with [Ca2+] values between 3 nM and 24.9 microm for [Ca+]-force relations. Measurements were taken on single saponin skinned muscle fiber preparations of BALB/c mice. Individual [Ca2+]force relations were characterized by the Ca2+ concentration at half-maximal force that indicates the sensitivity of the contractile proteins and by the steepness. Each force transient was transformed directly into a Ca2+ transient with respect to the individual [Ca2+]-force relation of the fiber. Results At 0.6 mM, single force transients induced by sevoflurane were lower compared with equimolar concentrations of isoflurane and halothane (P < 0.05). Similarly, calculated peak Ca2+ transients of sevoflurane were lower than those induced by equimolar halothane (P < 0.05). The Ca2+ concentrations at half maximal force were decreased after the addition of sevoflurane, isoflurane, and halothane in a concentration-dependent manner (P < 0.05). Conclusion Whereas sevoflurane, isoflurane, and halothane similarly increase the Ca2+ sensitivity of the contractile apparatus in skeletal muscle fibers, 0.6 mM sevoflurane induces smaller Ca2+ releases from the sarcoplasmic reticulum than does equimolar halothane.

Myocardial calcium cycling defect in furazolidone cardiomyopathy

1991 ◽  
Vol 69 (12) ◽  
pp. 1833-1840 ◽  
Author(s):  
Peter James O'Brien ◽  
Hua Shen ◽  
Janice E. Weiler ◽  
S. Mehdi Mirsalimi ◽  
Richard J. Julian
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Sarcoplasmic Reticulum ◽  
Ruthenium Red ◽  
Channel Activity ◽  
Release Channel ◽  
Calcium Sequestration ◽  
Pump Activity ◽  
Highly Correlated ◽  
Sarcoplasmic Reticulum Calcium

We have previously demonstrated that in furazolidone-induced congestive heart failure in turkeys the specific Ca2+-ATPase activity of myocardial sarcoplasmic reticulum (SR) is 60% increased in compensation for a 50% depression in net Ca2+-sequestration activity. This study tested the hypothesis that SR Ca2+-uptake and Ca2+-ATPase activities were uncoupled in this cardiomyopathy because of increased Ca2+-release channel activity. A novel microassay was used to monitor Ca2+ transport by myocardial homogenates using the fluorescent Ca2+ dye indo 1 to indicate extravesicular ionized Ca2+. The method is applied to cyropreserved biopsy specimens of myocardium and requires only 50 mg tissue. Both SR Ca2+-pump and SR Ca2+-channel activity were estimated using the channel-inhibitor ruthenium red (RR) and the mitochondrial inhibitor sodium azide. The specificity of the RR inhibition was confirmed using ryanodine. Cardiomyopathy was induced in 2-week-old turkey pouits by the addition of 0.07% furazolidone to their feed for 4 weeks. Compared with controls, myocardial maximal Ca2+-channel activity relative to maximal Ca2+-pump activity was 22% greater and duration of Ca2+-channel activity was 100% increased. However, the heart failure birds had 43 and 53% decreases in absolute maximal Ca2+-pumping and Ca2+-channel activities, respectively. The abnormal Ca2+-channel activity resulted in 200% greater time before initiation of net Ca2+ sequestration and 700% greater final myocardial Ca2+ concentrations. For all birds, the Ca2+-accumulating activity was highly correlated with Ca2+-release activity (all p < 0.05). These data indicate that in this animal model of congestive heart failure there is defective SR Ca2+-channel function resulting in abnormal Ca2+ homeostasis. However, this defect can only partially explain our previous finding of furazolidone-induced uncoupling of Ca2+ uptake from Ca2+-ATPase activities. The consequent myocardial Ca2+ overload predisposes the heart to fatigue and irreversible failure.Key words: sarcoplasmic reticulum, calcium sequestration, furazolidone cardiomyopathy, indo 1 spectrofluorometry.

scholarly journals Calcium Binding and Tension Development in Detergent-Treated Muscle Fibers

1974 ◽  
Vol 63 (2) ◽  
pp. 168-186 ◽  
Author(s):  
M. Orentlicher ◽  
J. P. Reuben ◽  
H. Grundfest ◽  
P. W. Brandt
Keyword(s):  
Binding Sites ◽  
Calcium Binding ◽  
Time Course ◽  
Muscle Fibers ◽  
Contractile Proteins ◽  
Tension Development ◽  
Brij 58 ◽  
Ca Uptake ◽  
Before And After ◽  
Nonionic Detergent

The nonionic detergent Brij 58 eliminates irreversibly the capability of the sarcoplasmic reticulum (SR) of skinned crayfish muscle fibers to sequester Ca and to release it under appropriate stimulation. In contrast to deoxycholate (DOC) which causes an irreversible diminution of tension as well, Brij 58 does not affect the contractile proteins. Comparison of the time-course of tension development before and after Brij treatment demonstrates that Ca is accessible to the contractile proteins more rapidly after the SR is destroyed but, nevertheless, much more slowly than is predicted for free diffusion of Ca in the myoplasm. Slowing apparently results because of the presence of ca 1 mmol/kg fiber of myoplasmic Ca-binding sites that remain after Ca uptake of the SR is eliminated. A theoretical model is presented which allows for the effects of binding sites and of an unstirred layer in the vicinity of the fiber on Ca diffusion into the myoplasm.

scholarly journals A slow component of intramembranous charge movement during sarcoplasmic reticulum calcium release in frog cut muscle fibers.

1996 ◽  
Vol 107 (1) ◽  
pp. 79-101 ◽  
Author(s):  
P C Pape ◽  
D S Jong ◽  
W K Chandler
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Rana Temporaria ◽  
Slow Component ◽  
Muscle Fibers ◽  
Charge Movement ◽  
Small Current ◽  
Sarcoplasmic Reticulum Calcium ◽  
A New Species ◽  
Peak Value

Cut muscle fibers from Rana temporaria were mounted in a double Vaseline-gap chamber and equilibrated with an end-pool solution that contained 20 mM EGTA and 1.76 mM Ca (sarcomere length, 3.3-3.8 microns; temperature, 14-16 degrees C). Sarcoplasmic reticulum (SR) Ca release, delta[CaT], was estimated from changes in myoplasmic pH (Pape, P.C., D.-S. Jong, and W.K. Chandler. 1995. J. Gen. Physiol. 106:259-336). The maximal value of delta[CaT] obtained during a depleting depolarization was assumed to equal the SR Ca content before stimulation, [CaSR]R (expressed as myoplasmic concentration). After a depolarization to -55 to -40 mV in fibers with [CaSR]R = 1,000-3,000 microM, currents from intramembranous charge movement, Icm, showed an early I beta component. This was followed by an I gamma hump, which decayed within 50 ms to a small current that was maintained for as long as 500 ms. This slow current was probably a component of Icm because the amount of OFF charge, measured after depolarizations of different durations, increased according to the amount of ON charge. Icm was also measured after the SR had been depleted of most of its Ca, either by a depleting conditioning depolarization or by Ca removal from the end pools followed by a series of depleting depolarizations. The early I beta component was essentially unchanged by Ca depletion, the I gamma hump was increased (for [CaSR]R &gt; 200 microM), the slow component was eliminated, and the total amount of OFF charge was essentially unchanged. These results suggest that the slow component of ON Icm is not movement of a new species of charge but is probably movement of Q gamma that is slowed by SR Ca release or some associated event such as the accompanying increase in myoplasmic free [Ca] that is expected to occur near the Ca release sites. The peak value of the apparent rate constant associated with this current, 2-4%/ms at pulse potentials between -48 and -40 mV, is decreased by half when [CaSR]R approximately equal to 500-1,000 microM, which gives a peak rate of SR Ca release of approximately 5-10 microM/ms.

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