Rabbit skeletal muscle sarcoplasmic reticulum Ca2+-ATPase activity: stimulation in vitro by thyroid hormone analogues and bipyridines

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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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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In vitro binding of dantrolene to sarcoplasmic reticulum of rabbit skeletal muscle

Biochemical Pharmacology ◽

10.1016/0006-2952(82)90328-8 ◽

1982 ◽

Vol 31 (6) ◽

pp. 965-968 ◽

Cited By ~ 11

Author(s):

Ahmad Reza Dehpour ◽

Siavoosh Mofakham ◽

Massoud Mahmoudian

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Rabbit Skeletal Muscle ◽

In Vitro Binding ◽

Vitro Binding

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Effect of anti-Ca2+-dependent ATPase sera on the Ca2+-dependent ATPase activity of rabbit skeletal muscle sarcoplasmic reticulum

Biochemical Society Transactions ◽

10.1042/bst0170671 ◽

1989 ◽

Vol 17 (4) ◽

pp. 671-673 ◽

Cited By ~ 1

Author(s):

KAY OHLENDIECK ◽

NORMA M. RYAN

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Atpase Activity ◽

Rabbit Skeletal Muscle ◽

Dependent Atpase

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N-ethylmaleimide-modified heavy meromyosin. A probe for actomyosin interactions.

The Journal of Cell Biology ◽

10.1083/jcb.82.1.57 ◽

1979 ◽

Vol 82 (1) ◽

pp. 57-65 ◽

Cited By ~ 63

Author(s):

R L Meeusen ◽

W Z Cande

Keyword(s):

Skeletal Muscle ◽

Atpase Activity ◽

Rabbit Skeletal Muscle ◽

Heavy Meromyosin ◽

Sulfhydryl Reagent ◽

Microtubule Polymerization ◽

Soil Amoeba ◽

Glycerinated Muscle

Treatment of rabbit skeletal muscle heavy meromyosin (HMM) with the sulfhydryl reagent N-ethylmaleimide (NEM) produces a species of HMM which remains tightly bound to actin in the presence of MgATP. NEM-HMM forms characteristic "arrowhead" complexes with actin which persist despite rinses with MgATP. NEM-HMM inhibits the actin activation of native HMM-ATPase activity, the superprecipitation of actomyosin, the contraction of glycerinated muscle myofibrils, and the contraction of cytoplasmic strands of the soil amoeba Chaos carolinensis. However, NEM-HMM does not interfere with in vitro microtubule polymerization or beating of demembranated cilia.

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