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.

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.

scholarly journals Adaptations in human muscle sarcoplasmic reticulum to prolonged submaximal training

2003 ◽  
Vol 94 (5) ◽  
pp. 2034-2042 ◽  
Author(s):  
H. J. Green ◽  
C. S. Ballantyne ◽  
J. D. MacDougall ◽  
M. A. Tarnopolsky ◽  
J. D. Schertzer
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Vastus Lateralis ◽  
Training Session ◽  
Maximal Activity ◽  
Hill Coefficient ◽  
Protein Levels ◽  
Plasmic Reticulum ◽  
Cycle Training ◽  
The Hill

In this study, we employed single-leg submaximal cycle training, conducted over a 10-wk period, to investigate adaptations in sarcoplasmic reticulum (SR) Ca2+-regulatory proteins and processes of the vastus lateralis. During the final weeks, the untrained volunteers (age 21.4 ± 0.3 yr; means ± SE, n = 10) were exercising 5 times/wk and for 60 min/session. Analyses were performed on tissue extracted by needle biopsy ∼4 days after the last training session. Compared with the control leg, the trained leg displayed a 19% reduction ( P < 0.05) in homogenate maximal Ca2+-ATPase activity (192 ± 11 vs. 156 ± 18 μmol · g protein−1 · min−1), a 4.3% increase ( P < 0.05) in pCa50, defined as the Ca2+ concentration at half-maximal activity (6.01 ± 0.05 vs. 6.26 ± 0.07), and no change in the Hill coefficient (1.75 ± 0.15 vs. 1.76 ± 0.21). Western blot analysis using monoclonal antibodies (7E6 and A52) revealed a 13% lower ( P < 0.05) sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 1 in trained vs. control in the absence of differences in SERCA2a. Training also resulted in an 18% lower ( P < 0.05) SR Ca2+ uptake and a 26% lower ( P < 0.05) Ca2+ release. It is concluded that a downregulation in SR Ca2+ cycling in vastus lateralis occurs with aerobic-based training, which at least in the case of Ca2+ uptake can be explained by reduction in Ca2+-ATPase activity and SERCA1 protein levels.

Comparative effects of a low-carbohydrate diet and exercise plus a low-carbohydrate diet on muscle sarcoplasmic reticulum responses in males

2006 ◽  
Vol 291 (4) ◽  
pp. C607-C617 ◽  
Author(s):  
T. A. Duhamel ◽  
H. J. Green ◽  
J. G. Perco ◽  
J. Ouyang
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Phase 1 ◽  
Hill Coefficient ◽  
Carbohydrate Diet ◽  
Low Carbohydrate Diet ◽  
Diet And Exercise ◽  
Low Carbohydrate ◽  
The Hill ◽  
The Relationship

We employed a glycogen-depleting session of exercise followed by a low-carbohydrate (CHO) diet to investigate modifications that occur in muscle sarcoplasmic reticulum (SR) Ca2+-cycling properties compared with low-CHO diet alone. SR properties were assessed in nine untrained males [peak aerobic power (V̇o2 peak) = 43.6 ± 2.6 (SE) ml·kg−1·min−1] during prolonged cycle exercise to fatigue performed at ∼58% V̇o2 peak after 4 days of low-CHO diet (Lo CHO) and after glycogen-depleting exercise plus 4 days of low-CHO (Ex+Lo CHO). Compared with Lo CHO, Ex+Lo CHO resulted in 12% lower ( P < 0.05) resting maximal Ca2+-ATPase activity ( Vmax = 174 ± 12 vs. 153 ± 10 μmol·g protein−1·min−1) and smaller reduction in Vmax induced during exercise. A similar effect was observed for Ca2+ uptake. The Hill coefficient, defined as slope of the relationship between cytosolic free Ca2+ concentration and Ca2+-ATPase activity, was higher ( P < 0.05) at rest (2.07 ± 0.15 vs. 1.90 ± 0.10) with Ex+Lo CHO, an effect that persisted throughout the exercise. The coupling ratio, defined as the ratio of Ca2+ uptake to Vmax, was 23–30% elevated ( P < 0.05) at rest and during the first 60 min of exercise with Ex+Lo CHO. The ∼27 and 34% reductions ( P < 0.05) in phase 1 and phase 2 Ca2+ release, respectively, observed during exercise with Lo CHO were not altered by Ex+Lo CHO. These results indicate that when prolonged exercise precedes a short-term Lo CHO diet, Ca2+ sequestration properties and efficiency are improved compared with those during Lo CHO alone.

Muscle sarcoplasmic reticulum calcium regulation in humans during consecutive days of exercise and recovery

2007 ◽  
Vol 103 (4) ◽  
pp. 1212-1220 ◽  
Author(s):  
T. A. Duhamel ◽  
R. D. Stewart ◽  
A. R. Tupling ◽  
J. Ouyang ◽  
H. J. Green
Keyword(s):  
Endoplasmic Reticulum ◽  
Sarcoplasmic Reticulum ◽  
Vastus Lateralis ◽  
Phase 1 ◽  
Regular Exercise ◽  
Phase 2 ◽  
Cycle Exercise ◽  
Tissue Samples ◽  
Sustained Reduction ◽  
Sarcoplasmic Reticulum Calcium

The study investigated the hypothesis that three consecutive days of prolonged cycle exercise would result in a sustained reduction in the Ca2+-cycling properties of the vastus lateralis in the absence of changes in the sarcoplasmic (endoplasmic) reticulum Ca2+-ATPase (SERCA) protein. Tissue samples were obtained at preexercise (Pre) and postexercise (Post) on day 1 (E1) and day 3 (E3) and during recovery day 1 (R1), day 2 (R2), and day 3 (R3) in 12 active but untrained volunteers (age 19.2 ± 0.27 yr; mean ± SE) and analyzed for changes (nmol·mg protein−1·min−1) in maximal Ca2+-ATPase activity ( Vmax), Ca2+ uptake and Ca2+ release (phase 1 and phase 2), and SERCA isoform expression (SERCA1a and SERCA2a). At E1, reductions ( P < 0.05) from Pre to Post in Vmax (150 ± 7 vs. 121 ± 7), Ca2+ uptake (7.79 ± 0.28 vs. 5.71 ± 0.33), and both phases of Ca2+ release (phase 1, 20.3 ± 1.3 vs. 15.2 ± 1.1; phase 2, 7.70 ± 0.60 vs. 4.99 ± 0.48) were found. In contrast to Vmax, which recovered at Pre E3 and then remained stable at Post E3 and throughout recovery, Ca2+ uptake remained depressed ( P < 0.05) at E3 Pre and Post and at R1 as did phase 2 of Ca2+ release. Exercise resulted in an increase ( P < 0.05) in SERCA1a (14% at R2) but not SERCA2a. It is concluded that rapidly adapting mechanisms protect Vmax following the onset of regular exercise but not Ca2+ uptake and Ca2+ release.

Malleability of human skeletal muscle sarcoplasmic reticulum to short-term training

2011 ◽  
Vol 36 (6) ◽  
pp. 904-912 ◽  
Author(s):  
Howard J. Green ◽  
Margaret Burnett ◽  
Helen Kollias ◽  
Jing Ouyang ◽  
Ian Smith ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Aerobic Power ◽  
Vastus Lateralis ◽  
Phase 1 ◽  
Type I ◽  
Phase 2 ◽  
Short Term ◽  
Tissue Samples ◽  
Participant Characteristics ◽  
Training Protocol

This study investigated the hypothesis that adaptations would occur in the sarcoplasmic reticulum in vastus lateralis soon after the onset of aerobic-based training consistent with reduced Ca2+-cycling potential. Tissue samples were extracted prior to (0 days) and following 3 and 6 days of cycling performed for 2 h at 60%–65% of peak aerobic power (VO2peak) in untrained males (VO2peak = 47 ± 2.3 mL·kg–1·min–1; mean ± SE, n = 6) and assessed for changes (nmol·mg protein–1·min–1) in maximal Ca2+-ATPase activity (Vmax), Ca2+-uptake, and Ca2+-release (phase 1 and phase 2) as well as the sarcoplasmic (endoplasmic) reticulum Ca2+-ATPase (SERCA) isoforms. Training resulted in reductions (p < 0.05) in SERCA1a at 6 days (–14%) but not at 3 days. For SERCA2a, reductions (p < 0.05) were also noted only at 6 days (–7%). For Vmax, depressions (p < 0.05) were found at 6 days (172 ± 11) but not at 3 days (176 ± 13; p < 0.10) compared with 0 days (192 ± 11). These changes were accompanied by a lower (p < 0.05) Ca2+-uptake at both 3 days (–39%) and 6 days (–48%). A similar pattern was found for phase 1 Ca2+-release with reductions (p < 0.05) of 37% observed at 6 days and 23% (p = 0.21) at 3 days of training, respectively. In a related study using the same training protocol and participant characteristics, microphotometric determinations of Vmax indicated reductions (p < 0.05) in type I at 3 days (–27%) and at 6 days (–34%) and in type IIA fibres at 6 days (–17%). It is concluded that in response to aerobic-based training, sarcoplasmic reticulum Ca2+-cycling potential is reduced by adaptations that occur soon after training onset.

Effects of 4-h ischemia and 1-h reperfusion on rat muscle sarcoplasmic reticulum function

2001 ◽  
Vol 281 (4) ◽  
pp. E867-E877 ◽  
Author(s):  
R. Tupling ◽  
H. Green ◽  
G. Senisterra ◽  
J. Lepock ◽  
N. McKee
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Phase 1 ◽  
Late Phase ◽  
Maximal Activity ◽  
Hill Coefficient ◽  
Sprague Dawley ◽  
Rapid Phase ◽  
Sprague Dawley Rats ◽  
The Hill

To investigate the hypothesis that ischemia and reperfusion would impair sarcoplasmic reticulum (SR) Ca2+ regulation in skeletal muscle, Sprague-Dawley rats ( n = 20) weighing 290 ± 3.5 g were randomly assigned to either a control control (CC) group, in which only the effects of anesthetization were studied, or to a group in which the muscles in one hindlimb were made ischemic for 4 h and allowed to recover for 1 h (I). The nonischemic, contralateral muscles served as control (C). Measurements of Ca2+-ATPase properties in homogenates and SR vesicles, in mixed gastrocnemius and tibialis anterior muscles, indicated no differences between groups on maximal activity, the Hill coefficient, and Ca50, defined as the Ca2+concentration needed to elicit 50% of maximal activity. In homogenates, Ca2+ uptake was lower ( P < 0.05) by 20–25%, measured at 0.5 and 1.0 μM of free Ca2+ ([Ca2+]f) in C compared with CC. In SR vesicles, Ca2+ uptake was lower ( P < 0.05) by 30–38% in I compared with CC at [Ca2+]f between 0.5 and 1.5 μM. Silver nitrate induced Ca2+ release, assessed during both the initial, early rapid ( phase 1), and slower, prolonged late ( phase 2) phases, in homogenates and SR vesicles, indicated a higher ( P < 0.05) release only in phase 1in SR vesicles in I compared with CC. These results indicate that the alterations in SR Ca2+ regulation, previously observed after prolonged ischemia by our group, are reversed within 1 h of reperfusion. However, the lower Ca2+ uptake observed in long-term, nonischemic homogenates suggests that altered regulation may occur in the absence of ischemia.

Human muscle sarcoplasmic reticulum function during submaximal exercise in normoxia and hypoxia

2004 ◽  
Vol 97 (1) ◽  
pp. 180-187 ◽  
Author(s):  
T. A. Duhamel ◽  
H. J. Green ◽  
J. G. Perco ◽  
S. D. Sandiford ◽  
J. Ouyang
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Vastus Lateralis ◽  
Maximal Activity ◽  
Human Muscle ◽  
Hill Coefficient ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Moderate Intensity Exercise ◽  
Dependent Atpase

In this study, the response of the sarcoplasmic reticulum (SR) to prolonged exercise, performed in normoxia (inspired O2 fraction = 0.21) and hypoxia (inspired O2 fraction = 0.14) was studied in homogenates prepared from the vastus lateralis muscle in 10 untrained men (peak O2 consumption = 3.09 ± 0.25 l/min). In normoxia, performed at 48 ± 2.2% peak O2 consumption, maximal Ca2+-dependent ATPase activity was reduced by ∼25% at 30 min of exercise compared with rest (168 ± 10 vs. 126 ± 8 μmol·g protein−1·min−1), with no further reductions observed at 90 min (129 ± 6 μmol·g protein−1·min−1). No changes were observed in the Hill coefficient or in the Ca2+ concentration at half-maximal activity. The reduction in maximal Ca2+-dependent ATPase activity at 30 min of exercise was accompanied by oxalate-dependent reductions ( P < 0.05) in Ca2+ uptake by ∼20% (370 ± 22 vs. 298 ± 25 μmol·g protein−1·min−1). Ca2+ release, induced by 4-chloro- m-cresol and assessed into fast and slow phases, was decreased ( P < 0.05) by ∼16 and ∼32%, respectively, by 90 min of exercise. No differences were found between normoxia and hypoxia for any of the SR properties examined. It is concluded that the disturbances induced in SR Ca2+ cycling with prolonged moderate-intensity exercise in human muscle during normoxia are not modified when the exercise is performed in hypoxia.

Methods for determining cardiac sarcoplasmic reticulum Ca2+ pump kinetics from fura 2 measurements

1994 ◽  
Vol 267 (4) ◽  
pp. C1145-C1151 ◽  
Author(s):  
M. E. Kargacin ◽  
G. J. Kargacin
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Membrane Vesicles ◽  
Hill Coefficient ◽  
General Applicability ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Raw Data ◽  
Tissue Samples ◽  
Fura 2 ◽  
Uptake Velocity ◽  
The Hill

We explored the use of four methods for analyzing real and simulated fura 2 measurements of Ca2+ uptake by membrane vesicles derived from the sarcoplasmic reticulum (SR) of cardiac muscle. Uptake velocity was calculated 1) directly from the raw data, 2) after segmenting the raw data and averaging the data points in each segment, 3) after smoothing of the raw data by moving-window averaging, and 4) by Savitsky-Golay convolution. Methods 2, 3, and 4 could be used to determine maximum uptake velocity, the Hill coefficient, and the Ca2+ concentration at half-maximal pump velocity from Ca2+ concentration vs. time and velocity curves that were too noisy to analyze directly. Data analysis using these methods should have general applicability to biological experiments, especially those in which large numbers of measurements are made. The fluorometric method we describe for measuring Ca2+ uptake by cardiac SR vesicles opens up the possibility of studying SR function from very small starting tissue samples.

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.

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