EFFECTS OF ECCENTRIC CONTRACTIONS ON IN VITRO Na+-K+-ATPase ACTIVITY AND SARCOPLASMIC RETICULUM Ca2+-SEQUESTERING IN RAT SKELETAL MUSCLE

The role of prolonged electrical stimulation on sarcoplasmic reticulum (SR) Ca2+sequestration measured in vitro and muscle energy status in fast white and red skeletal muscle was investigated. Fatigue was induced by 90 min intermittent 10-Hz stimulation of rat gastrocnemius muscle, which led to reductions (p < 0.05) in ATP, creatine phosphate, and glycogen of 16, 55, and 49%, respectively, compared with non-stimulated muscle. Stimulation also resulted in increases (p < 0.05) in muscle lactate, creatine, Pi, total ADP, total AMP, IMP, and inosine. Calculated free ADP (ADPf) and free AMP (AMPf) were elevated 3- and 15-fold, respectively. No differences were found in the metabolic response between tissues obtained from the white (WG) and red (RG) regions of the gastrocnemius. No significant reductions in SR Ca2+ATPase activity were observed in homogenate (HOM) or a crude SR fraction (CM) from WG or RG muscle following exercise. Maximum Ca2+uptake in HOM and CM preparations was similar in control (C) and stimulated (St) muscles. However, Ca2+uptake at 400 nM free Ca2+was significantly reduced in CM from RG (0.108 ± 0.04 to 0.076 ± 0.02 μmol∙mg−1protein∙min−1in RG–C and RG–St, respectively). Collectively, these data suggest that reductions in muscle energy status are dissociated from changes in SR Ca2+ATPase activity in vitro but are related to Ca2+uptake at physiological free [Ca2+] in fractionated SR from highly oxidative muscle. Dissociation of SR Ca2+ATPase activity from Ca2+uptake may reflect differences in the mechanisms evaluated by these techniques.Key words: sarcoplasmic reticulum, contractile activity, Ca2+sequestration, energy status, red and white gastrocnemius.

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PO-252 Effect of acupuncture intervention on the changes of cytoplasmic and mitochondrial Ca2+ concentration following eccentric contractions in rat skeletal muscle

Exercise Biochemistry Review ◽

10.14428/ebr.v1i5.11003 ◽

2018 ◽

Vol 1 (5) ◽

Author(s):

Aishan Liu ◽

Fangming Liu ◽

Xuelin Zhang ◽

Yarong Wang ◽

Mei Kong ◽

...

Keyword(s):

Skeletal Muscle ◽

Electrical Stimulation ◽

Fluorescent Imaging ◽

Eccentric Contractions ◽

Rat Skeletal Muscle ◽

Tetanic Force ◽

Acupuncture Intervention ◽

Stimulation Group

Objective The purpose of this study was to evaluate the effect of acupuncture intervention on the changes of cytoplasmic and mitochondrial Ca2+ concentration following eccentric contractions (ECC) in rat skeletal muscle. Methods 24 healthy male Wistar rats were randomly divided into 4 groups: control group (C, n=6)、electrical stimulation group (E, n=6)、electrical stimulation group with acupuncture intervention (EA, n=6)、electrical stimulation group with acupuncture +TRP channel inhibitor Gd3+ (EAI, n=6). The animal model of eccentric induced skeletal muscle injury was established by electrical stimulation on spinotrapezius muscle of anaesthetised rats in vivo, that is to say, the intact spinotrapezius muscle of adult Wistar rats was exteriorized, and tetanic eccentric contractions (100 Hz, 10 sets of 50 contractions) were elicited by electrical stimulation during synchronized muscle stretch of 10% resting muscle length. Cytoplasmic Ca2+ accumulation were determined by loading the muscle with fura 4-AM using fluorescent imaging in vivo, and mitochondrial Ca2+ concentration were determined by loading the muscle with fura 2-AM using fluorescent imaging in vitro, and recorded changes of muscle maximum tetanic force. Results (1) In vivo, compared with the C , cytoplasmic Ca2+ accumulation increased more rapidly during ECC in the E (P < 0.001). Acupuncture intervention significantly reduced cytosolic Ca2+ accumulation in the EA compared with the E (P < 0.01), and we discovered that muscle deformation generated by acupuncture intervention induced a robust Ca2+ spark response confined in close spatial proximity to the sarcolemmal membrane in intact muscle fibers. Although no significant differences between the EA and EAI, Gd3+ abolished the majority of cytoplasmic Ca2+ accumulation decrease during ECC in the EAI and a robust Ca2+ spark response disappeared compared with the EA. (2) In vitro, compared with the C, mitochondrial Ca2+ concentration did not elevations in MCC in the E. EA cytoplasmic Ca2+ increased rapidly above the C and E (P < 0.01), respectively, but EAI significantly attenuated the increases in mitochondrial Ca2+ concentration compared with the EA (P < 0.01). (3). Compared with the C , maximum tetanic force was significantly lower in the E after ECC (P < 0.01). EA maximum tetanic force increased rapidly compared with the E after ECC (P < 0.05), but EAL abolished the majority maximum tetanic force increase after ECC (P < 0.05). Conclusions (1)Eccentric contraction caused cytoplasmic Ca2+ accumulation, but mitochondrial Ca2+ concentration decrease. (2)Acupuncture can effectively reduce cytosolic Ca2+ overload, following by mitochondrial Ca2+ concentration increase , which in turn abnormally high cytoplasmic Ca2+ levels are buffed by the mitochondria, and improved muscle function, and the effect was associated to the TRP channels.

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Maintenance of structural and functional characteristics of skeletal-muscle mitochondria and sarcoplasmic-reticular membranes after chronic ethanol treatment

Biochemical Journal ◽

10.1042/bj2740565 ◽

1991 ◽

Vol 274 (2) ◽

pp. 565-573 ◽

Cited By ~ 24

Author(s):

F Cardellach ◽

T F Taraschi ◽

J S Ellingson ◽

C D Stubbs ◽

E Rubin ◽

...

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Atpase Activity ◽

Order Parameter ◽

Chronic Ethanol ◽

Muscle Mitochondria ◽

Skeletal Muscle Mitochondria ◽

Ethanol Feeding

The effect of long-term ethanol intake on the structural and functional characteristics of rat skeletal-muscle mitochondria and sarcoplasmic reticulum was investigated. Functionally, skeletal-muscle mitochondria were characterized by a high respiratory control index and ADP/O ratio and a high State-3 respiration rate with different substrates. These parameters were not significantly different in preparations from control and ethanol-fed rats, except for a small increase in the rate of oxidation of alpha-oxoglutarate/malate in the latter. In submitochondrial particles from the two groups of animals there was no significant difference in cytochrome content, ATPase activity or the activity of respiratory-chain complexes. Mitochondrial membranes from untreated and ethanol-fed rats showed no difference in the baseline e.s.r. order parameter, and both preparations were equally sensitive to disordering by ethanol in vitro. Similarly, sarcoplasmic-reticulum preparations were not significantly affected by long-term ethanol feeding with respect to Ca2(+)-ATPase activity or in baseline order parameter and susceptibility to membrane disordering by ethanol in vitro. These membranes were also equally sensitive to degradation by exogenous phospholipase A2. Ethanol feeding did not alter the class composition of mitochondrial or sarcoplasmic-reticulum membrane phospholipids, nor the acyl composition of individual phospholipid classes. Specifically, the changes in acyl composition that characteristically occur in liver microsomal phosphatidylinositol and liver mitochondrial cardiolipin were not observed in the corresponding phospholipids from skeletal-muscle membranes. In experiments where membrane preparations from liver and skeletal muscle from the same ethanol-fed animals were compared, the liver membranes developed membrane tolerance, with the muscle membranes retaining normal sensitivity to disordering effects by ethanol. It is concluded that: (a) different tissues from the same animals differ in their susceptibility to ethanol; (b) the tissue-specific lack of development of membrane tolerance correlates with a lack of chemical changes in the phospholipids and with a retention of normal function of mitochondria and sarcoplasmic reticulum; (c) effects of chronic ethanol intake on muscle function are not due to a defect in the mitochondrial energy supply.

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THE EFFECTS OF ISCHEMIA ON SARCOPLASMIC RETICULUM Ca2+-ATPase ACTIVITY ARE ALTERED IN RAT SKELETAL MUSCLE PREPARED WITH DTT.

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-199905001-00726 ◽

1999 ◽

Vol 31 (Supplement) ◽

pp. S166 ◽

Cited By ~ 2

Author(s):

R. Tupling ◽

H. Green ◽

N. McKee

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Atpase Activity ◽

Rat Skeletal Muscle

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Characteristics of sarcoplasmic reticulum from normal and denervated rat skeletal muscle

Biochemical Journal ◽

10.1042/bj2000011 ◽

1981 ◽

Vol 200 (1) ◽

pp. 11-15 ◽

Cited By ~ 11

Author(s):

G N Palexas ◽

N Savage ◽

H Isaacs

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Atpase Activity ◽

Calcium Transport ◽

Membrane Structure ◽

Calcium Content ◽

Heterogeneous Population ◽

Rat Skeletal Muscle ◽

Vesicle Size ◽

Dependent Atpase

Denervation of rat skeletal muscle produces after 14 days a decrease in Ca2+ uptake of a heterogeneous population of sarcoplasmic-reticulum vesicles, when measured in the presence of oxalate. The Mg2+-dependent ATPase (Ca2+-independent) activity increased after the same period and the Ca2+ + Mg2+-dependent ATPase activity decreased. Concomitant with these changes, there was an increase in vesicle size and calcium content. The observations are discussed in terms of changes in altered membrane structure, manifested in the shift of the equilibrium of the ATPase from an enzyme involved in calcium transport to a phosphoenzyme giving rise to an increase in the Mg2+-dependent ATPase activity.

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Na+-K+-ATPase in rat skeletal muscle: muscle fiber-specific differences in exercise-induced changes in ion affinity and maximal activity

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.90760.2008 ◽

2009 ◽

Vol 296 (1) ◽

pp. R125-R132 ◽

Cited By ~ 33

Author(s):

Carsten Juel

Keyword(s):

Skeletal Muscle ◽

Atpase Activity ◽

Muscle Fiber ◽

Muscle Activity ◽

Fiber Type ◽

Treadmill Running ◽

Vitro Activity ◽

In Vitro Activity ◽

Rat Skeletal Muscle

It is unclear whether muscle activity reduces or increases Na+-K+-ATPase maximal in vitro activity in rat skeletal muscle, and it is not known whether muscle activity changes the Na+-K+-ATPase ion affinity. The present study uses quantification of ATP hydrolysis to characterize muscle fiber type-specific changes in Na+-K+-ATPase activity in sarcolemmal membranes and in total membranes obtained from control rats and after 30 min of treadmill running. ATPase activity was measured at Na+ concentrations of 0–80 mM and K+ concentrations of 0–10 mM. Km and Vmax values were obtained from a Hill plot. Km for Na+ was higher (lower affinity) in total membranes of glycolytic muscle (extensor digitorum longus and white vastus lateralis), when compared with oxidative muscle (red gastrocnemius and soleus). Treadmill running induced a significant decrease in Km for Na+ in total membranes of glycolytic muscle, which abolished the fiber-type difference in Na+ affinity. Km for K+ (in the presence of Na+) was not influenced by running. Running only increased the maximal in vitro activity ( Vmax) in total membranes from soleus, whereas Vmax remained constant in the three other muscles tested. In conclusion, muscle activity induces fiber type-specific changes both in Na+ affinity and maximal in vitro activity of the Na+-K+-ATPase. The underlying mechanisms may involve translocation of subunits and increased association between PLM units and the αβ complex. The changes in Na+-K+-ATPase ion affinity are expected to influence muscle ion balance during muscle contraction.

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Sodium plus Potassium-Activated, Ouabain-Inhibited AdenosineTriphosphatase from a Fraction of Rat Skeletal Muscle, and Lack of Insulin Effect on It

The Journal of General Physiology ◽

10.1085/jgp.54.2.188 ◽

1969 ◽

Vol 54 (2) ◽

pp. 188-202 ◽

Cited By ~ 33

Author(s):

Ellen Rogus ◽

Thomas Price ◽

Kenneth L. Zierler

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Enzyme System ◽

Human Muscle ◽

Rat Skeletal Muscle ◽

Ph Optimum ◽

Insulin Effect ◽

Na Efflux

An ATPase, activated by Na+ plus K+ in the presence of Mg++ and inhibited by ouabain, has been obtained from rat skeletal muscle. Unlike ATPase's with similar properties obtained from other preparations, this ATPase was found only in the fraction containing fragmented sarcoplasmic reticulum. It is suggested that in rat skeletal muscle this ATPase may reside in sarcoplasmic reticulum and not in sarcolemma. This ATPase differed in its pH optimum and in its cation sensitivity from that of rat brain and from that of human muscle reported by Samaha and Gergely (1965, 1966). Because insulin accelerates Na+ efflux from muscle, efforts were made to determine whether or not this effect of insulin could be attributed to increased Na+ + K+-activated ATPase activity. Insulin, administered either in vivo or in vitro, had no demonstrable effect on the enzyme system, nor did it protect against inhibition by ouabain.

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