Changes in inorganic phosphate and force production in human skeletal muscle after cast immobilization

2005 ◽  
Vol 98 (1) ◽  
pp. 307-314 ◽  
Author(s):  
Neeti Pathare ◽  
Glenn A. Walter ◽  
Jennifer E. Stevens ◽  
Zhaohui Yang ◽  
Enyi Okerke ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Magnetic Resonance ◽  
Inorganic Phosphate ◽  
Force Production ◽  
Resonance Spectroscopy ◽  
Specific Force ◽  
Phosphate Content ◽  
Cast Immobilization ◽  
Resting Energy

Cast immobilization is associated with decreases in muscle contractile area, specific force, and functional ability. The pathophysiological processes underlying the loss of specific force production as well as the role of metabolic alterations are not well understood. The aim of this study was to quantify changes in the resting energy-rich phosphate content and specific force production after immobilization.31P-magnetic resonance spectroscopy, three-dimensional magnetic resonance imaging, and isometric strength testing were performed in healthy subjects and patients with an ankle fracture after 7 wk of immobilization and during rehabilitation. Muscle biopsies were obtained in a subset of patients. After immobilization, there was a significant decrease in the specific plantar flexor torque and a significant increase in the inorganic phosphate (Pi) concentration ( P < 0.001) and the Pi-to-phosphocreatine (PCr) ratio ( P < 0.001). No significant change in the PCr content or basal pH was noted. During rehabilitation, both the Picontent and the Pi-to-PCr ratio decreased and specific torque increased, approaching control values after 10 wk of rehabilitation. Regression analysis showed an inverse relationship between the in vivo Piconcentration and specific torque ( r = 0.65, P < 0.01). In vitro force mechanics performed on skinned human muscle fibers demonstrated that varying the Pilevels within the ranges observed across individuals in vivo (4–10 mM) changed force production by ∼16%. In summary, our findings clearly depict a change in the resting energy-rich phosphate content of skeletal muscle with immobilization, which may negatively impact its force generation.

scholarly journals Introduction to in vivo31P magnetic resonance spectroscopy of (human) skeletal muscle

1999 ◽  
Vol 58 (4) ◽  
pp. 861-870 ◽  
Author(s):  
A. Heerschap ◽  
C. Houtman ◽  
H. J. A. in 't Zandt ◽  
A. J. van den Bergh ◽  
B. Wieringa
Keyword(s):  
Skeletal Muscle ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Current Status ◽  
Resonance Spectroscopy ◽  
Biochemical Processes ◽  
Non Invasive ◽  
Introductory Overview ◽  
Muscle Biochemistry

31P magnetic resonance spectroscopy (MRS) offers a unique non-invasive window on energy metabolism in skeletal muscle, with possibilities for longitudinal studies and of obtaining important bioenergetic data continuously and with sufficient time resolution during muscle exercise. The present paper provides an introductory overview of the current status of in vivo31P MRS of skeletal muscle, focusing on human applications, but with some illustrative examples from studies on transgenic mice. Topics which are described in the present paper are the information content of the 31P magnetic resonance spectrum of skeletal muscle, some practical issues in the performance of this MRS methodology, related muscle biochemistry and the validity of interpreting results in terms of biochemical processes, the possibility of investigating reaction kinetics in vivo and some indications for fibre-type heterogeneity as seen in spectra obtained during exercise.

Studies of the dynamics of skeletal muscle regeneration: the mouse came back!

1998 ◽  
Vol 76 (1) ◽  
pp. 13-26 ◽  
Author(s):  
Judy E Anderson
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Muscle Fiber ◽  
Muscle Regeneration ◽  
Skeletal Muscle Regeneration ◽  
Resonance Spectroscopy ◽  
Dystrophic Mouse

Regeneration of skeletal muscle tissue includes sequential processes of muscle cell proliferation and commitment, cell fusion, muscle fiber differentiation, and communication between cells of various tissues of origin. Central to the process is the myosatellite cell, a quiescent precursor cell located between the mature muscle fiber and its sheath of external lamina. To form new fibers in a muscle damaged by disease or direct injury, satellite cells must be activated, proliferate, and subsequently fuse into an elongated multinucleated cell. Current investigations in the field concern modulation of the effectiveness of skeletal muscle regeneration, the regeneration-specific role of myogenic regulatory gene expression distinct from expression during development, the impact of growth and scatter factors and their respective receptors in amplifying precursor numbers, and promoting fusion and maturation of new fibers and the ultimate clinical therapeutic applications of such information to alleviate disease. One approach to muscle regeneration integrates observations of muscle gene expression, proliferation, myoblast fusion, and fiber growth in vivo with parallel studies of cell cycling behaviour, endocrine perturbation, and potential biochemical markers of steps in the disease-repair process detected by magnetic resonance spectroscopy techniques. Experiments on muscles from limb, diaphragm, and heart of the mdx dystrophic mouse, made to parallel clinical trials on human Duchenne muscular dystrophy, help to elucidate mechanisms underlying the positive treatment effects of the glucocorticoid drug deflazacort. This review illustrates an effective combination of in vivo and in vitro experiments to integrate the distinctive complexities of post-natal myogenesis in regeneration of skeletal muscle tissue.Key words: satellite cell, cell cycling, HGF/SF, c-met receptor, MyoD, myogenin, magnetic resonance spectroscopy, mdx dystrophic mouse, deflazacort.

Effect of insulin on intracellular pH and phosphate metabolism in human skeletal muscle in vivo

1991 ◽  
Vol 81 (1) ◽  
pp. 123-128 ◽  
Author(s):  
D. J. Taylor ◽  
S. W. Coppack ◽  
T. A. D. Cadoux-Hudson ◽  
G. J. Kemp ◽  
G. K. Radda ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Ph ◽  
Inorganic Phosphate ◽  
Human Skeletal Muscle ◽  
Muscle Metabolism ◽  
Normal Subjects ◽  
Phosphate Concentration ◽  
Resonance Spectroscopy ◽  
Phosphorus Containing

1. 31P nuclear magnetic resonance spectroscopy and the hyperinsulinaemic-euglycaemic clamp were used simultaneously to assess the effect of insulin on intracellular pH and the major phosphorus-containing metabolites of normal human skeletal muscle in vivo in four normal subjects. 2. Insulin and glucose were infused for 120 min. Plasma insulin increased approximately 10-fold over pre-clamp levels (5.6 ± 0.9 m-units/l pre-clamp and 54 ± 5 m-units/l over the last hour of infusion; mean ± sem, n = 4). Plasma glucose concentration did not change significantly (5.4 ± 0.2 mmol/l pre-clamp and 5.5 ± 0.1 mmol/l over the last hour of infusion). 3. Insulin and glucose infusion resulted in a decline in the intracellular pH of forearm muscle of 0.027 ± 0.007 unit/h (P < 0.01), whereas in control studies of the same subjects, pH rose by 0.046 ± 0.005 unit/h (P < 0.001). 4. In the clamp studies, intracellular inorganic phosphate concentration rose by 18%/h, whereas ATP, phosphocreatine and phosphomonoester concentrations did not change. In plasma, inorganic phosphate concentration was 1.16 ± 0.05 mmol/l before infusion, and this decreased by a mean rate of 0.14 mmol h−1 l−1. No change was observed in any of these intracellular metabolites in the control studies. 5. The results show that, under physiological conditions, insulin does not raise intracellular pH in human muscle, and thus cannot influence muscle metabolism by this mechanism. The results also suggest that insulin causes a primary increase in the next flux of inorganic phosphate across the muscle cell membrane.

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