Ca2+ Uptake Coupled to Glycogen Phosphorolysis in the Glycogenolytic-Sarcoplasmic Reticulum Complex from Rat Skeletal Muscle

1996 ◽  
Vol 51 (7-8) ◽  
pp. 591-598 ◽  
Author(s):  
M. Nogues ◽  
A. Cuenda ◽  
F. Henao ◽  
C. Gutiérrez-Merino
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Glycogen Phosphorylase ◽  
Rat Skeletal Muscle ◽  
Subcellular Structure ◽  
Sequential Action ◽  
Physiological Conditions ◽  
Low Concentrations ◽  
Ischemic Muscle ◽  
Stimulation Of

Abstract The glycogenolytic-sarcoplasmic reticulum complex from rat skeletal muscle accumulates Ca2+ upon stimulation of glycogen phosphorolysis in the absence of added ATP. It is shown that an efficient Ca2+ uptake involves the sequential action of glycogen phosphorylase, phosphoglucomutase and hexokinase, which generate low concentrations of ATP (approximately 1 -2 μм) compartmentalized in the immediate vicinity of the sarcoplasmic reticulum Ca2+, Mg2+-ATPase (the Ca2+ pump). The Ca2+ uptake supported by glycogenolysis in this subcellular structure is strongly stimulated by micromolar concentrations of AMP, showing that the glycogen phosphorylase associated with this complex is in the dephosphorylated b form. The results point out that the flux through this compartmentalized metabolic pathway should be enhanced in physiological conditions leading to increased AMP concentrations in the sarcoplasm, such as long-lasting contractions and in ischemic muscle.

scholarly journals Ca-ATPase isozyme expression in sarcoplasmic reticulum is altered by chronic stimulation of skeletal muscle

FEBS Letters ◽  
1990 ◽  
Vol 259 (2) ◽  
pp. 269-272 ◽  
Author(s):  
F.Norman Briggs ◽  
K.Francis Lee ◽  
Joseph J. Feher ◽  
Andrew S. Wechsler ◽  
Kay Ohiendieck ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Chronic Stimulation ◽  
Stimulation Of

scholarly journals Reversible ATP-induced inactivation of branched-chain 2-oxo acid dehydrogenase

1980 ◽  
Vol 192 (1) ◽  
pp. 155-163 ◽  
Author(s):  
R Odessey
Keyword(s):  
Skeletal Muscle ◽  
Liver Mitochondria ◽  
Initial Activity ◽  
Rat Skeletal Muscle ◽  
Kidney Mitochondria ◽  
Physiological Conditions ◽  
Acid Dehydrogenase ◽  
Skeletal Muscle Mitochondria ◽  
Branched Chain

The branched chain 2-oxo acid dehydrogenase from rat skeletal muscle, heart, kidney and liver mitochondria can undergo a reversible activation-inactivation cycle in vitro. Similar results were obtained with the enzyme from kidney mitochondria of pig and cow. The dehydrogenase is markedly inhibited by ATP and the inhibition is not reversed by removing the nucleotide. The non-metabolizable ATP analogue adenosine 5′-[beta gamma-imido] triphosphate can block the effect of ATP when added with the nucleotide, but has no effect by itself, nor can it reverse the inhibition in mitochondria preincubated with ATP. These findings suggest that the branched chain 2-oxo acid dehydrogenase undergoes a stable modification that requires the splitting of the ATP gamma-phosphate group. In skeletal muscle mitochondria the rate of inhibition by ATP is decreased by oxo acid substrates and enhanced by NADH. The dehydrogenase can be reactivated 10-20 fold by incubation at pH 7.8 in a buffer containing Mg2+ and cofactors. Reactivation is blocked by NaF (25 mM). The initial activity of dehydrogenase extracted from various tissues of fed rats varies considerably. Activity is near maximal in kidney and liver whereas the dehydrogenase in heart and skeletal muscle is almost completely inactivated. These studies emphasize that comparisons of branched chain 2-oxo acid dehydrogenase activity under various physiological conditions or in different tissues must take into account its state of activation. Thus the possibility exists that the branched chain 2-oxo acid dehydrogenase may be physiologically regulated via a covalent mechanism.

Effects of endogenous calcium transport inhibitor from heart muscle on the active calcium uptake and passive calcium release properties of sarcoplasmic reticulum

1989 ◽  
Vol 67 (9) ◽  
pp. 999-1006 ◽  
Author(s):  
Njanoor Narayanan ◽  
Philip Bedard ◽  
Trilochan S. Waraich
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Heart Muscle ◽  
Calcium Release ◽  
Membrane Vesicles ◽  
Transport Inhibitor ◽  
Low Concentrations ◽  
Active Calcium ◽  
High Concentrations ◽  
Stimulation Of

In the present study, the effects of the cytosolic Ca2+ transport inhibitor on ATP-dependent Ca2+ uptake by, and unidirectional passive Ca2+ release from, sarcoplassmic reticulum enriched membrane vesicles were examined in parallel experiments to determine whether inhibitor-mediated enhancement in Ca2+ efflux contributes to inhibition of net Ca2+ uptake. When assays were performed at pH 6.8 in the presence of oxalate, low concentrations (<100 μg/mL) of the inhibitor caused substantial inhibition of Ca2+ uptake by SR (28–50%). At this pH, low concentrations of the inhibitor did not cause enhancement of passive Ca2+ release from actively Ca2+-loaded sarcoplasmic reticulum. Under these conditions, high concentrations (>100 μg/mL) of the inhibitor caused stimulation of passive Ca2+ release but to a much lesser extent when compared with the extent of inhibition of active Ca2+ uptake (i.e., twofold greater inhibition of Ca2+ uptake than stimulation of Ca2+ release). When Ca2+ uptake and release assays were carried out at pH 7.4, the Ca2+ release promoting action of the inhibitor became more pronounced, such that the magnitude of enhancement in Ca2+ release at varying concentrations of the inhibitor (20–200 μg/mL) was not markedly different from the magnitude of inhibition of Ca2+ uptake. In the absence of oxalate in the assay medium, inhibition of Ca2+ uptake was observed at alkaline but not acidic pH. These findings imply that the inhibition of Ca2+ uptake observed at pH 6.8 is mainly due to decrease in the rate of active Ca2+ transport into the membrane vesicles rather than stimulation of passive Ca2+ efflux; at alkaline pH (pH 7.4), enhanced Ca2+ efflux contributes substantially, if not exclusively, to the decrease in Ca2+ uptake observed in the presence of the inhibitor. It is suggested that if the cytosolic inhibitor has actions similar to those observed in vitro in intact cardiac muscle, acid–base status of the intracellular fluid would be a major factor influencing the nature of its effects (inhibition of Ca2+ uptake or stimulation of Ca2+ release) on transmembrane Ca2+ fluxes across the sarcoplasmic reticulum.Key words: sarcoplasmic reticulum, Ca2+ uptake, Ca2+ release, endogenous inhibitor, heart muscle.

Insulin increases thermogenesis in rat skeletal muscle following exercise

1985 ◽  
Vol 248 (1) ◽  
pp. E148-E151
Author(s):  
T. W. Balon ◽  
A. Zorzano ◽  
M. N. Goodman ◽  
N. B. Ruderman
Keyword(s):  
Skeletal Muscle ◽  
Insulin Secretion ◽  
Glycogen Synthesis ◽  
O2 Consumption ◽  
Rat Skeletal Muscle ◽  
Additional Energy ◽  
Rat Muscle ◽  
Prior Exercise ◽  
Increase Insulin Secretion ◽  
Stimulation Of

Insulin increased O2 consumption in isolated perfused rat muscle for upward of 2 h after a treadmill run. Insulin did not increase O2 consumption in nonexercised rats, nor did prior exercise increase O2 consumption in the absence of added insulin. The stimulation of glycogen synthesis by insulin was also enhanced in muscle of previously exercised rats. The additional energy required for this was not sufficient to account for the increase in O2 consumption, however. The results indicate that insulin increases thermogenesis in skeletal muscle after exercise. They also raise the possibility that in intact organisms the thermogenic effect of foods that increase insulin secretion could be increased by prior exercise.

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