Preservation of sarcoplasmic reticulum Ca2+-sequestering function in homogenates of different fibre type composition following sprint activity

1994 ◽  
Vol 72 (10) ◽  
pp. 1231-1237 ◽  
Author(s):  
J. Dossett-Mercer ◽  
H. J. Green ◽  
E. Chin ◽  
F. Grange
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Dry Weight ◽  
Muscle Fibre Types ◽  
Glycogen Depletion ◽  
Fibre Type Composition ◽  
Fibre Composition ◽  
Type Composition ◽  
Male Wistar Rats

To examine the effect of exercise on sarcoplasmic reticulum function in muscle tissue of different fibre composition, adult male Wistar rats weighing 388 ± 23 g (x ± SE) ran intermittently on a treadmill until fatigue. Fatigue was induced by 15–20 min of running performed at 52 m/min on an 8° incline in periods of 2.5 min of exercise separated by 2 min of recovery. Analysis of sarcoplasmic reticulum Ca2+ ATPase activity determined in homogenates indicated no difference (p > 0.05) between age-matched control and exercised tissue for the soleus (SOL; 0.121 ± 0.012 vs. 0.156 ± 0.018 μmol∙mg−1 protein∙min−1), red gastrocnemius (RG; 0.381 ± 0.022 vs. 0.354 ± 0.022), or white gastrocnemius (WG; 0.526 ± 0.05 vs. 0.471 ± 0.031). Similarly, both total ATPase and Mg2+ ATPase activities were unaffected by the exercise in any of the tissues examined. Exercise also failed to alter sarcoplasmic reticulum Ca2+ uptake in homogenates of the SOL (1.43 ± 0.15 vs. 1.38 ± 0.19 nmol∙mg−1 protein∙min−1), RG (3.74 ± 0.29 vs. 3.59 ± 0.24), and WG (5.98 ± 0.48 vs. 5.41 ± 0.50). At fatigue, glycogen depletion was similar in all tissue types and amounted to 65.1% in the SOL (172 ± 9 vs. 60 ± 16 mmol∙glucosyl units−1∙kg−1 dry weight), 74.4% in RG (164 ± 8 vs. 42 ± 6), and 79% in the WG (167 ± 9 vs. 35 ± 9). It is concluded that exercise by itself does not alter sarcoplasmic reticulum Ca2+-sequestering function in tissues of primarily different fibre composition when determined in homogenates in vitro. The integrity of sarcoplasmic reticulum function is preserved despite an apparent extensive recruitment of all tissue types during the exercise.Key words: sarcoplasmic reticulum function, Ca2+ uptake, Ca2+ ATPase activity, muscle fibre types.

scholarly journals Selective innervation of types of fibres in developing rat muscle

1987 ◽  
Vol 132 (1) ◽  
pp. 249-263
Author(s):  
W. J. Thompson ◽  
L. C. Soileau ◽  
R. J. Balice-Gordon ◽  
L. A. Sutton
Keyword(s):  
Motor Units ◽  
Neonatal Rat ◽  
Muscle Fibre Types ◽  
Muscle Fibres ◽  
Glycogen Depletion ◽  
Fibre Type Composition ◽  
Type Composition ◽  
Motor Neurones ◽  
Developing Rat ◽  
Polyneuronal Innervation

The technique of glycogen depletion has been used to identify the types of muscle fibres innervated by individual motor neurones in the neonatal rat. This analysis shows that neonatal motor units are highly biased in their fibre type composition, even at times when the fibres receive extensive polyneuronal innervation. This finding suggests that the innervation of muscle fibres is somehow sorted according to type during early development. This sorting does not appear to occur during the removal of the polyneuronal innervation because little, if any, increase in the bias of unit compositions occurs as the number of synapses present in the muscle is reduced 2- to 3-fold. To determine whether the sorted innervation might be explained by a selective synaptogenesis, a study was made of the type compositions of units formed by reinnervation of neonatal soleus muscle. Glycogen depletion of single units 2 weeks following crush of the soleus nerve at postnatal day 2 showed that most of them (10/12) had biased type compositions which could not be explained by a random reinnervation. The location of fibres in the reinnervated motor units suggests that the regenerating axons innervated a novel set of fibres. The differentiation of fibres into types was apparently not changed during their reinnervation. These results imply that regenerating motor neurones in the neonatal rat selectively reinnervate muscle fibre types. These and other studies further imply that the organization of fibres into motor units during normal development does not occur, as is widely believed, by a random innervation of naive fibres and their subsequent differentiation under the influence of innervation.

Na+-K+-ATPase in rat skeletal muscle: content, isoform, and activity characteristics

2004 ◽  
Vol 96 (1) ◽  
pp. 316-326 ◽  
Author(s):  
J. R. Fowles ◽  
H. J. Green ◽  
J. Ouyang
Keyword(s):  
Atpase Activity ◽  
Fiber Type ◽  
Hydrolytic Activity ◽  
Ouabain Binding ◽  
Equal Distribution ◽  
Atpase Assay ◽  
Type Composition ◽  
Activity Measurements ◽  
Male Wistar Rats

The purpose of this study was to investigate the hypothesis that muscle Na+-K+-ATPase activity is directly related to Na+-K+-ATPase content and the content of the α2-catalytic isoform in muscles of different fiber-type composition. To investigate this hypothesis, tissue was sampled from soleus (Sol), red gastrocnemius (RG), white gastrocnemius (WG), and extensor digitorum longus (EDL) muscles at rest from 38 male Wistar rats weighing 413 ± 6.0 g (mean ± SE). Na+-K+-ATPase activity was determined in homogenates (Hom) and isolated crude membranes (CM) by the regenerating ouabain-inhibitable hydrolytic activity assay (ATPase) and the 3- O-methylfluorescein K+-stimulated phosphatase (3- O-MFPase) assay in vitro. In addition, Na+-K+-ATPase content (Bmax) and the distribution of α1-, α2-, β1-, and β2-isoforms were determined by [3H]ouabain binding and Western blot, respectively. For the ATPase assay, differences ( P < 0.05) in enzyme activity between muscles were observed in Hom (EDL > WG) and in CM (Sol > EDL = WG). For the 3- O-MFPase assay, differences ( P < 0.05) were also found for Hom (Sol > RG = EDL > WG) and CM (Sol = WG > RG). For Bmax, differences in the order of RG = EDL > Sol = WG ( P < 0.05) were observed. Isoform distribution was similar between Hom and CM and indicated in CM, a greater density ( P < 0.05) of α1 in Sol than WG and EDL ( P < 0.05), but more equal distribution of α2 between muscles. The β1 was greater ( P < 0.05) in Sol and RG, and the β2 was greater in EDL and WG ( P < 0.05). Over all muscles, the correlation ( r) between Hom 3- O-MFPase and Bmax was 0.45 ( P < 0.05) and between Hom α2 and Bmax, 0.59 ( P < 0.05). The α1 distribution correlated to Hom 3- O-MFPase ( r = 0.79, P < 0.05) CM ATPase ( r = 0.69, P < 0.005) and CM 3- O-MFPase activity ( r = 0.32, P < 0.05). The α2 distribution was not correlated with any of the Na+-K+-ATPase activity measurements. The results indicate generally poor relationships between activity and total pump content and α2 isoform content of the Na+-K+-ATPase. Several factors, including the type of preparation and the type of assay, appear important in this regard.

Role of sarcoplasmic reticulum in loss of load-sensitive relaxation in pressure overload cardiac hypertrophy

1994 ◽  
Vol 266 (1) ◽  
pp. H68-H78 ◽  
Author(s):  
C. R. Cory ◽  
R. W. Grange ◽  
M. E. Houston
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Hypertrophy ◽  
Atpase Activity ◽  
Pressure Overload ◽  
Fold Increase ◽  
Left Ventricular ◽  
Isometric Tension ◽  
Tension Development ◽  
Sequestration Potential

The loss of load-sensitive relaxation observed in the pressure-overloaded heart may reflect a strategy of slowed cytosolic Ca2+ uptake to yield a prolongation of the active state of the muscle and a decrease in cellular energy expenditure. A decrease in the potential of the sarcoplasmic reticulum (SR) to resequester cytosolic Ca2+ during diastole could contribute to this attenuated load sensitivity. To test this hypothesis, both in vitro mechanical function of anterior papillary muscles and the SR Ca2+ sequestration potential of female guinea pig left ventricle were compared in cardiac hypertrophy (Hyp) and sham-operated (Sham) groups. Twenty-one days of pressure overload induced by coarctation of the suprarenal, subdiaphragmatic aorta resulted in a 36% increase in left ventricular mass in the Hyp. Peak isometric tension, the rate of isometric tension development, and the maximal rates of isometric and isotonic relaxation were significantly reduced in Hyp. Load-sensitive relaxation were significantly reduced in Hyp. Load-sensitive relaxation quantified by the ratio of a rapid loading to unloading force step in isotonically contracting papillary muscle was reduced 50% in Hyp muscles. Maximum activity of SR Ca(2+)-adenosinetriphosphatase (ATPase) measured under optimal conditions (37 degrees C; saturating Ca2+) was unaltered, but at low free Ca2+ concentrations (0.65 microM), it was decreased by 43% of the Sham response. Bivariate regression analysis revealed a significant (r = 0.84; P = 0.009) relationship between the decrease in SR Ca(2+)-ATPase activity and the loss of load-sensitive relaxation after aortic coarctation. Stimulation of the SR Ca(2+)-ATPase by the catalytic subunit of adenosine 3',5'-cyclic monophosphate-dependent protein kinase resulted in a 2.6-fold increase for Sham but only a 1.6-fold increase for Hyp. Semiquantitative Western blot radioimmunoassays revealed that the changes in SR Ca(2+)-ATPase activity were not due to decreases in the content of the Ca(2+)-ATPase protein or phospholamban. Our data directly implicate a role for decreased SR function in attenuated load sensitivity. A purposeful downregulation of SR Ca2+ uptake likely results from a qualitative rather than a quantitative change in the ATPase and possibly one of its key regulators, phospholamban.

Effects of prior exercise and a low-carbohydrate diet on muscle sarcoplasmic reticulum function during cycling in women

2006 ◽  
Vol 101 (3) ◽  
pp. 695-706 ◽  
Author(s):  
T. A. Duhamel ◽  
H. J. Green ◽  
J. G. Perco ◽  
J. Ouyang
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Vastus Lateralis ◽  
Phase 1 ◽  
Vastus Lateralis Muscle ◽  
Low Carbohydrate Diet ◽  
Hill Slope ◽  
Low Carbohydrate ◽  
Exercise Induced

The effects of exercise and diet on sarcoplasmic reticulum Ca2+-cycling properties in female vastus lateralis muscle were investigated in two groups of women following four different conditions. The conditions were 4 days of a low-carbohydrate (Lo CHO) and glycogen-depleting exercise plus a Lo CHO diet (Ex + Lo CHO) ( experiment 2) and 4 days of normal CHO (Norm CHO) and glycogen-depleting exercise plus Norm CHO (Ex + Norm CHO) ( experiment 1). Peak aerobic power (V̇o2peak) was 38.1 ± 1.4 (SE); n = 9 and 35.6 ± 1.4 ml·kg−1·min−1; n = 9, respectively. Sarcoplasmic reticulum properties measured in vitro in homogenates (μmol·g protein−1·min−1) indicated exercise-induced reductions ( P < 0.05) in maximal Ca2+-ATPase activity (0 > 30, 60 min > fatigue), Ca2+ uptake (0 > 30 > 60 min, fatigue), and Ca2+ release, both phase 1 (0, 30 > 60 min, fatigue) and phase 2 (0 > 30, 60 min, fatigue; 30 min > fatigue) in Norm CHO. Exercise was without effect in altering the Hill slope ( nH), defined as the slope of relationship between Ca2+-ATPase activity and Ca2+ concentration. No differences were observed between Norm CHO and Ex+Norm CHO. Compared with Norm CHO, Lo CHO resulted in a lower ( P < 0.05) Ca2+ uptake, phase 1 Ca2+ release (30 min), and nH. Ex + Lo CHO resulted in a greater ( P < 0.05) Ca2+ uptake and nH compared with Lo CHO. The results demonstrate that Lo CHO alone can disrupt SR Ca2+ cycling and that, with the exception of Ca2+ release, a glycogen-depleting session of exercise before Lo CHO can reverse the effects.

Effects of prolonged low frequency stimulation on skeletal muscle sarcoplasmic reticulum

1995 ◽  
Vol 73 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
E. R. Chin ◽  
H. J Green ◽  
F. Grange ◽  
J. Dossett-Mercer ◽  
P. J. O'Brien
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Metabolic Response ◽  
Contractile Activity ◽  
Creatine Phosphate ◽  
Energy Status ◽  
Muscle Lactate ◽  
Muscle Energy

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.

Ischemia-induced alterations in sarcoplasmic reticulum Ca(2+)-ATPase activity in rat soleus and EDL muscles

1996 ◽  
Vol 271 (6) ◽  
pp. C1942-C1948 ◽  
Author(s):  
H. J. Green ◽  
N. H. McKee ◽  
A. J. Carvalho ◽  
J. C. Dossett-Mercer
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Time Course ◽  
Extensor Digitorum Longus ◽  
Fiber Type ◽  
Time Dependent ◽  
Fiber Type Composition ◽  
Type Composition ◽  
Edl Muscle ◽  
Muscle Fiber Type Composition

To investigate the time-dependent effects of ischemia, as modified by muscle fiber type composition, on sarcoplasmic reticulum (SR) function, Ca(2+)-ATPase activity (total minus basal) was measured in homogenates prepared from samples obtained from rat soleus and extensor digitorum longus (EDL) muscle of ischemic and contralateral controls. Ischemia was induced by occlusion of blood flow to one hindlimb for periods of 1, 2, and 3 h (n = 10 per group). In EDL, maximal Ca(2+)-ATPase activity (expressed in mumol.g wet wt-1.min-1) was higher (P < 0.05) in ischemic than in control at 1 h (80 +/- 10 vs. 56.5 +/- 5.3) and increased progressively with ischemia at both 2 h (88 +/- 4.6 vs. 53.1 +/- 2.8) and 3 h (116 +/- 3.8 vs. 67.8 +/- 3.2). In contrast, in soleus, increases (P < 0.05) in Ca(2+)-ATPase activity with ischemia were observed at 2 h (19.2 +/- 0.86 vs. 14.0 +/- 0.56) and 3 h (19.9 +/- 1.4 vs. 12.4 +/- 0.62) but not at 1 h (10.7 +/- 1.5 vs. 10.0 +/- 0.83). In both EDL and soleus, basal Mg(2+)-ATPase was unchanged with ischemia. On the basis of these findings, it can be concluded that ischemia results in an increase in the maximal SR Ca(2+)-ATPase activity but that the time course of the change is dependent on the fiber type composition of the muscle.

Muscle sarcoplasmic reticulum Ca2+ cycling adaptations during 16 h of heavy intermittent cycle exercise

2005 ◽  
Vol 99 (3) ◽  
pp. 836-843 ◽  
Author(s):  
G. P. Holloway ◽  
H. J. Green ◽  
T. A. Duhamel ◽  
S. Ferth ◽  
J. W. Moule ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Vastus Lateralis ◽  
Phase 1 ◽  
Hill Coefficient ◽  
Kinetic Properties ◽  
Cycle Exercise ◽  
Tissue Samples ◽  
The Hill

The repetition-dependent effects of a repetitive heavy exercise protocol previously shown to alter muscle mechanic behavior (Green HJ, Duhamel TA, Ferth S, Holloway GP, Thomas MM, Tupling AR, Rich SM, and Yau JE. J Appl Physiol 97: 2166–2175, 2004) on muscle sarcoplasmic reticulum (SR) Ca2+-transport properties, measured in vitro, were examined in 12 untrained volunteers [peak aerobic power (V̇o2 peak) = 44.3 ± 0.66 ml·kg−1·min−1]. The protocol involved 6 min of cycle exercise performed at ∼91% V̇o2 peak once per hour for 16 h. Tissue samples were obtained from the vastus lateralis before (B) and after (A) exercise at repetitions 1 (R1), 2 (R2), 9 (R9), and 16 (R16). Reductions ( P < 0.05) in maximal Ca2+-ATPase activity ( Vmax) of 26 and 12% with exercise were only observed at R1 and R16, respectively. Vmax remained depressed ( P < 0.05) at R2 (B) but not at R9 (B) and R16 (B). No changes were observed in two other kinetic properties of the enzyme, namely the Hill coefficient (defined as the slope of the relationship between Ca2+-ATPase activity and free Ca2+ concentration) and the Ca50 (defined as the free Ca2+ concentration needed to elicit 50% Vmax). Changes in Ca2+ uptake (measured at 2,000 nM) with exercise and recovery generally paralleled Vmax. The apparent coupling ratio, defined as the ratio between Ca2+ uptake and Vmax, was unaffected by the intermittent protocol. Reductions ( P < 0.05) in phase 1 Ca2+ release (32%) were only observed at R1. No differences were observed between B and A for R2, R9, and R16 or between B and B for R1, R2, R9, and R16. The changes in phase 2 Ca2+ release were as observed for phase 1 Ca2+ release. It is concluded that the SR Ca2+-handling properties, in general, display rapid adaptations to repetitive exercise.

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