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A century of exercise physiology: key concepts in muscle cell volume regulation. Eur J Appl Physiol 2022; 122:541-559. [PMID: 35037123 DOI: 10.1007/s00421-021-04863-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 11/27/2021] [Indexed: 12/13/2022]
Abstract
Skeletal muscle cells can both gain and lose volume during periods of exercise and rest. Muscle cells do not behave as perfect osmometers because the cell volume changes are less than predicted from the change in extracellular osmolality. Therefore, there are mechanisms involved in regulating cell volume, and they are different for regulatory volume decreases and regulatory volume increases. Also, after an initial rapid change in cell volume, there is a gradual and partial recovery of cell volume that is effected by ion and water transport mechanisms. The mechanisms have been studied in non-contracting muscle cells, but remain to be fully elucidated in contracting muscle. Changes in muscle cell volume are known to affect the strength of contractile activity as well as anabolic/catabolic signaling, perhaps indicating that cell volume should be a regulated variable in skeletal muscle cells. Muscles contracting at moderate to high intensity gain intracellular volume because of increased intracellular osmolality. Concurrent increases in interstitial (extracellular) muscle volume occur from an increase in osmotically active molecules and increased vascular filtration pressure. At the same time, non-contracting muscles lose cell volume because of increased extracellular (blood) osmolality. This review provides the physiological foundations and highlights key concepts that underpin our current understanding of volume regulatory processes in skeletal muscle, beginning with consideration of osmosis more than 200 years ago and continuing through to the process of regulatory volume decrease and regulatory volume increase.
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2
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Cass JA, Williams CD, Irving TC, Lauga E, Malingen S, Daniel TL, Sponberg SN. A mechanism for sarcomere breathing: volume change and advective flow within the myofilament lattice. Biophys J 2021; 120:4079-4090. [PMID: 34384761 DOI: 10.1016/j.bpj.2021.08.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 06/19/2021] [Accepted: 08/04/2021] [Indexed: 11/28/2022] Open
Abstract
During muscle contraction, myosin motors anchored to thick filaments bind to and slide actin thin filaments. These motors rely on energy derived from ATP, supplied, in part, by diffusion from the sarcoplasm to the interior of the lattice of actin and myosin filaments. The radial spacing of filaments in this lattice may change or remain constant during contraction. If the lattice is isovolumetric, it must expand when the muscle shortens. If, however, the spacing is constant or has a different pattern of axial and radial motion, then the lattice changes volume during contraction, driving fluid motion and assisting in the transport of molecules between the contractile lattice and the surrounding intracellular space. We first create an advective-diffusive-reaction flow model and show that the flow into and out of the sarcomere lattice would be significant in the absence of lattice expansion. Advective transport coupled to diffusion has the potential to substantially enhance metabolite exchange within the crowded sarcomere. Using time-resolved x-ray diffraction of contracting muscle, we next show that the contractile lattice is neither isovolumetric nor constant in spacing. Instead, lattice spacing is time varying, depends on activation, and can manifest as an effective time-varying Poisson ratio. The resulting fluid flow in the sarcomere lattice of synchronous insect flight muscles is even greater than expected for constant lattice spacing conditions. Lattice spacing depends on a variety of factors that produce radial force, including cross-bridges, titin-like molecules, and other structural proteins. Volume change and advective transport varies with the phase of muscle stimulation during periodic contraction but remains significant at all conditions. Although varying in magnitude, advective transport will occur in all cases in which the sarcomere is not isovolumetric. Akin to "breathing," advective-diffusive transport in sarcomeres is sufficient to promote metabolite exchange and may play a role in the regulation of contraction itself.
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Affiliation(s)
- Julie A Cass
- Allen Institute for Cell Science, Seattle, Washington; Department of Biology, University of Washington, Seattle, Washington
| | - C David Williams
- Department of Biology, University of Washington, Seattle, Washington; Applied ML Group, Microsoft CSE, Redmond, Washington
| | - Thomas C Irving
- BioCAT and CSRRI, Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Sage Malingen
- Department of Biology, University of Washington, Seattle, Washington
| | - Thomas L Daniel
- Department of Biology, University of Washington, Seattle, Washington.
| | - Simon N Sponberg
- School of Physics & School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia.
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3
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Willwacher S, Sleboda DA, Mählich D, Brüggemann GP, Roberts TJ, Bratke G. The time course of calf muscle fluid volume during prolonged running. Physiol Rep 2021; 8:e14414. [PMID: 32378332 PMCID: PMC7202985 DOI: 10.14814/phy2.14414] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/16/2020] [Indexed: 01/30/2023] Open
Abstract
Muscle fluid is essential for the biochemistry and the biomechanics of muscle contraction. Here, we provide evidence that muscle fluid volumes undergo significant changes during 75 min of moderate intensity (2.7 ± 0.4 m/s) running. Using MRI measurements at baseline and after 2.5, 5, 10, 15, 45 and 75 min, we found that the volumes of calf muscles (quantified through average cross‐sectional area) in 18 young recreational runners increase (up to 9% in the gastrocnemii) at the beginning and decrease (below baseline levels) at later stages of running. However, the intensity of changes varied between analyzed muscles. We speculate that these changes are induced by muscle activity and dehydration‐related changes in osmotic pressure gradients between intramuscular and extramuscular spaces. These findings highlight the complex nature of muscle fluid shifts during prolonged running exercise.
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Affiliation(s)
- Steffen Willwacher
- Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany.,School of Human Movement and Nutrition Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - David A Sleboda
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - Daniela Mählich
- Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany
| | - Gert-Peter Brüggemann
- Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany
| | - Thomas J Roberts
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - Grischa Bratke
- Department of Diagnostic and Interventional Radiology, University of Cologne, Cologne, Germany
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4
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Morel B, Hug F, Nordez A, Pournot H, Besson T, Mathevon L, Lapole T. Reduced Active Muscle Stiffness after Intermittent Submaximal Isometric Contractions. Med Sci Sports Exerc 2020; 51:2603-2609. [PMID: 31269006 DOI: 10.1249/mss.0000000000002080] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE Whether muscle stiffness is influenced by fatigue remains unclear. Classical methods used to assess muscle stiffness provide a global measure at the joint level. As fatigue may selectively affect specific muscles, a joint-level approach may not be sensitive enough to detect potential changes in muscle stiffness. Taking advantage of ultrasound shear wave elastography, this study aimed to determine the influence of a fatiguing protocol involving intermittent submaximal isometric contractions on muscle shear modulus (an index of stiffness). METHODS Shear modulus was measured on either the vastus lateralis (n = 9) or the abductor digiti minimi (n = 10) before and after 15 min of intermittent submaximal isometric contractions at 60% of maximal voluntary contraction (MVC) (4 s ON, 4 s OFF). An index of active muscle stiffness was estimated PRE- and POST-fatigue as the slope of the linear regression established between shear modulus and absolute joint force up to 60% MVC. RESULTS After the fatiguing exercise, MVC was significantly decreased by 22% ± 7% and 32% ± 15% for knee extension and little finger abduction, respectively (P < 0.001). When compared to PRE-fatigue, the index of active muscle stiffness was 12% ± 15% lower for the vastus lateralis (P < 0.031) and 44% ± 19% lower for the abductor digiti minimi (P < 0.001) POST-fatigue. CONCLUSIONS Although the present results cannot clearly determine the involved mechanisms, they demonstrate a decreased active muscle stiffness after a fatiguing task involving intermittent submaximal isometric contractions. Further studies should now determine whether this change in stiffness affects performance and risk of injury.
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Affiliation(s)
- Baptiste Morel
- University of Saint-Etienne, Inter-university Laboratory of Human Movement Science, University of Lyon, Saint-Etienne, FRANCE.,Laboratory "Movement, Interactions, Performance," Faculty of Sciences and Technologies, Department of Sport Sciences, Le Mans University, Le Mans, FRANCE
| | - François Hug
- Laboratory "Movement, Interactions, Performance," Faculty of Sport Sciences, University of Nantes, Nantes, FRANCE.,Institut Universitaire de France, Paris, FRANCE
| | - Antoine Nordez
- Laboratory "Movement, Interactions, Performance," Faculty of Sport Sciences, University of Nantes, Nantes, FRANCE.,Health and Rehabilitation Research Institute, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, NEW ZEALAND
| | - Hervé Pournot
- University of Saint-Etienne, Inter-university Laboratory of Human Movement Science, University of Lyon, Saint-Etienne, FRANCE
| | - Thibault Besson
- University of Saint-Etienne, Inter-university Laboratory of Human Movement Science, University of Lyon, Saint-Etienne, FRANCE
| | - Laure Mathevon
- University of Saint-Etienne, Inter-university Laboratory of Human Movement Science, University of Lyon, Saint-Etienne, FRANCE
| | - Thomas Lapole
- University of Saint-Etienne, Inter-university Laboratory of Human Movement Science, University of Lyon, Saint-Etienne, FRANCE
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Chalchat E, Gennisson JL, Peñailillo L, Oger M, Malgoyre A, Charlot K, Bourrilhon C, Siracusa J, Garcia-Vicencio S. Changes in the Viscoelastic Properties of the Vastus Lateralis Muscle With Fatigue. Front Physiol 2020; 11:307. [PMID: 32390859 PMCID: PMC7194212 DOI: 10.3389/fphys.2020.00307] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 03/19/2020] [Indexed: 12/31/2022] Open
Abstract
We investigated the in vivo effects of voluntary fatiguing isometric contractions of the knee extensor muscles on the viscoelastic properties of the vastus lateralis (VL). Twelve young males (29.0 ± 4.5 years) performed an intermittent voluntary fatigue protocol consisting of 6 sets × 10 repetitions of 5-s voluntary maximal isometric contractions with 5-s passive recovery periods between repetitions. Voluntary and evoked torque were assessed before, immediately after, and 20 min after exercise. The shear modulus (μ) of the VL muscle was estimated at rest and during a ramped isometric contraction using a conventional elastography technique. An index of active muscle stiffness was then calculated (slope from the relationship between shear modulus and absolute torque). Resting muscle viscosity (η) was quantified using a shear-wave spectroscopy sequence to measure the shear-wave dispersion. Voluntary and evoked torque decreased by ∼37% (P < 0.01) immediately after exercise. The resting VL μ was lower at the end of the fatigue protocol (-57.9 ± 5.4%, P < 0.001), whereas the resting VL η increased (179.0 ± 123%, P < 0.01). The active muscle stiffness index also decreased with fatigue (P < 0.05). By 20 min post-fatigue, there were no significant differences from the pre-exercise values for VL η and the active muscle stiffness index, contrary to the resting VL μ. We show that the VL μ is greatly reduced and η greatly enhanced by fatigue, reflecting a more compliant and viscous muscle. The quantification of both shear μ and η moduli in vivo may contribute to a better understanding of the mechanical behavior of muscles during fatigue in sports medicine, as well as in clinical situations.
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Affiliation(s)
- Emeric Chalchat
- Unité de Physiologie de l'Exercice et des Activités en Conditions Extrêmes, Département Environnements Opérationnels, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
| | - Jean-Luc Gennisson
- BIOMAPS, Laboratoire d'Imagerie Biomédicale Multi-Modale, CEA, Université Paris-Saclay, CNRS UMR 9011, INSERM UMR 1281, Orsay, France
| | - Luis Peñailillo
- Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Finis Terrae University, Santiago, Chile
| | - Myriam Oger
- Unité Imagerie, Département des Plateformes et Recherche Technologique, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
| | - Alexandra Malgoyre
- Unité de Physiologie de l'Exercice et des Activités en Conditions Extrêmes, Département Environnements Opérationnels, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,LBEPS, Univ Evry, IRBA, Université Paris Saclay, Evry, France
| | - Keyne Charlot
- Unité de Physiologie de l'Exercice et des Activités en Conditions Extrêmes, Département Environnements Opérationnels, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,LBEPS, Univ Evry, IRBA, Université Paris Saclay, Evry, France
| | - Cyprien Bourrilhon
- Unité de Physiologie de l'Exercice et des Activités en Conditions Extrêmes, Département Environnements Opérationnels, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,LBEPS, Univ Evry, IRBA, Université Paris Saclay, Evry, France
| | - Julien Siracusa
- Unité de Physiologie de l'Exercice et des Activités en Conditions Extrêmes, Département Environnements Opérationnels, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,LBEPS, Univ Evry, IRBA, Université Paris Saclay, Evry, France
| | - Sebastian Garcia-Vicencio
- Unité de Physiologie de l'Exercice et des Activités en Conditions Extrêmes, Département Environnements Opérationnels, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,LBEPS, Univ Evry, IRBA, Université Paris Saclay, Evry, France
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Williams CD, Salcedo MK, Irving TC, Regnier M, Daniel TL. The length-tension curve in muscle depends on lattice spacing. Proc Biol Sci 2013; 280:20130697. [PMID: 23843386 DOI: 10.1098/rspb.2013.0697] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Classic interpretations of the striated muscle length-tension curve focus on how force varies with overlap of thin (actin) and thick (myosin) filaments. New models of sarcomere geometry and experiments with skinned synchronous insect flight muscle suggest that changes in the radial distance between the actin and myosin filaments, the filament lattice spacing, are responsible for between 20% and 50% of the change in force seen between sarcomere lengths of 1.4 and 3.4 µm. Thus, lattice spacing is a significant force regulator, increasing the slope of muscle's force-length dependence.
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Affiliation(s)
- C David Williams
- Department of Physiology and Biophysics, University of Washington, , Seattle, WA, USA.
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7
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Kristensen M, Juel C. Potassium-transporting proteins in skeletal muscle: cellular location and fibre-type differences. Acta Physiol (Oxf) 2010; 198:105-23. [PMID: 19769637 DOI: 10.1111/j.1748-1716.2009.02043.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Abstract Potassium (K(+)) displacement in skeletal muscle may be an important factor in the development of muscle fatigue during intense exercise. It has been shown in vitro that an increase in the extracellular K(+) concentration ([K(+)](e)) to values higher than approx. 10 mm significantly reduce force development in unfatigued skeletal muscle. Several in vivo studies have shown that [K(+)](e) increases progressively with increasing work intensity, reaching values higher than 10 mm. This increase in [K(+)](e) is expected to be even higher in the transverse (T)-tubules than the concentration reached in the interstitium. Besides the voltage-sensitive K(+) (K(v)) channels that generate the action potential (AP) it is suggested that the big-conductance Ca(2+)-dependent K(+) (K(Ca)1.1) channel contributes significantly to the K(+) release into the T-tubules. Also the ATP-dependent K(+) (K(ATP)) channel participates, but is suggested primarily to participate in K(+) release to the interstitium. Because there is restricted diffusion of K(+) to the interstitium, K(+) released to the T-tubules during AP propagation will be removed primarily by reuptake mediated by transport proteins located in the T-tubule membrane. The most important protein that mediates K(+) reuptake in the T-tubules is the Na(+),K(+)-ATPase alpha(2) dimers, but a significant contribution of the strong inward rectifier K(+) (Kir2.1) channel is also suggested. The Na(+), K(+), 2Cl(-) 1 (NKCC1) cotransporter also participates in K(+) reuptake but probably mainly from the interstitium. The relative content of the different K(+)-transporting proteins differs in oxidative and glycolytic muscles, and might explain the different [K(+)](e) tolerance observed.
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Affiliation(s)
- M Kristensen
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2200, Copenhagen N, Denmark.
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8
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Cermak NM, LeBlanc PJ, Peters SJ, Vandenboom R, Roy BD. Effect of extracellular osmolality on metabolism in contracting mammalian skeletal muscle in vitro. Appl Physiol Nutr Metab 2009; 34:1055-64. [DOI: 10.1139/h09-106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Extensive research has been conducted on hepatocyte metabolism perturbed under the influence of anisosmotic stress. However, much less is known about the behaviour of skeletal muscle metabolism under similar conditions. After establishing a working model to study anisosmotic stress in resting mammalian skeletal muscle, the current study tested the hypothesis that hyperosmotic (HYPER) stress would lead to increased creatine, lactate, and measured enzyme activity, whereas hypo-osmotic (HYPO) stress would lead to decreased metabolites and enzyme activity vs. iso-osmotic (ISO) stress post contraction. Rat soleus (SOL) and extensor digitorum longus (EDL) were isolated and incubated in an organ bath (95% O2, 5% CO2, pH 7.4, 25 °C) altered to targeted osmotic conditions (ISO, 290 osmol·L–1; HYPO, 180 osmol·L–1; HYPER, 400 osmol·L–1). Muscle samples were flash frozen after 10 min of contraction. Post contraction, muscle water content in the SOL HYPO condition was 18% greater than ISO, and HYPER had approximately 14% less water content than ISO (p < 0.05). In the HYPO condition, EDL had 21% greater water content than ISO, and HYPER had 17% less water content than ISO (p < 0.05). SOL HYPO resulted in higher phosphocreatine and lower lactate and creatine vs. HYPER (p < 0.05) but there were no differences in EDL between HYPO and HYPER. Pyruvate dehydrogenase activity increased in SOL HYPER vs. HYPO, whereas glycogen phosphorylase a increased in EDL HYPER vs. HYPO. In conclusion, fibre-type-specific responses exist after contraction such that when SOL muscle is perturbed in HYPER, as compared with HYPO, media, metabolic activity increases. Future work should focus on glucose uptake–regulation during anisosmotic conditions.
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Affiliation(s)
- Naomi M. Cermak
- Centre for Muscle Metabolism and Biophysics, Department of Physical Education and Kinesiology, Faculty of Applied Health Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
| | - Paul J. LeBlanc
- Centre for Muscle Metabolism and Biophysics, Department of Physical Education and Kinesiology, Faculty of Applied Health Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
| | - Sandra J. Peters
- Centre for Muscle Metabolism and Biophysics, Department of Physical Education and Kinesiology, Faculty of Applied Health Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
| | - Rene Vandenboom
- Centre for Muscle Metabolism and Biophysics, Department of Physical Education and Kinesiology, Faculty of Applied Health Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
| | - Brian D. Roy
- Centre for Muscle Metabolism and Biophysics, Department of Physical Education and Kinesiology, Faculty of Applied Health Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
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9
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Abstract
Regulation of cell volume is a fundamental property of all animal cells and is of particular importance in skeletal muscle where exercise is associated with a wide range of cellular changes that would be expected to influence cell volume. These complex electrical, metabolic and osmotic changes, however, make rigorous study of the consequences of individual factors on muscle volume difficult despite their likely importance during exercise. Recent charge-difference modelling of cell volume distinguishes three major aspects to processes underlying cell volume control: (i) determination by intracellular impermeant solute; (ii) maintenance by metabolically dependent processes directly balancing passive solute and water fluxes that would otherwise cause cell swelling under the influence of intracellular membrane-impermeant solutes; and (iii) volume regulation often involving reversible short-term transmembrane solute transport processes correcting cell volumes towards their normal baselines in response to imposed discrete perturbations. This review covers, in turn, the main predictions from such quantitative analysis and the experimental consequences of comparable alterations in extracellular pH, lactate concentration, membrane potential and extracellular tonicity. The effects of such alterations in the extracellular environment in resting amphibian muscles are then used to reproduce the intracellular changes that occur in each case in exercising muscle. The relative contributions of these various factors to the control of cell volume in resting and exercising skeletal muscle are thus described.
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10
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Oliver SR, Wright VP, Parinandi N, Clanton TL. Thermal tolerance of contractile function in oxidative skeletal muscle: no protection by antioxidants and reduced tolerance with eicosanoid enzyme inhibition. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1695-705. [PMID: 18768765 DOI: 10.1152/ajpregu.90429.2008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mechanisms for the loss of muscle contractile function in hyperthermia are poorly understood. This study identified the critical temperature, resulting in a loss of contractile function in isolated diaphragm (thermal tolerance), and then tested the hypotheses 1) that increased reactive oxygen species (ROS) production contributes to the loss of contractile function at this temperature, and 2) eicosanoid metabolism plays an important role in preservation of contractile function in hyperthermia. Contractile function and passive force were measured in rat diaphragm bundles during and after 30 min of exposure to 40, 41, 42 or 43 degrees C. Between 40 and 42 degrees C, there were no effects of hyperthermia, but at 43 degrees C, a significant loss of active force and an increase in passive force were observed. Inhibition of ROS with the antioxidants, Tiron or Trolox, did not inhibit the loss of contractile force at 43 degrees C. Furthermore, treatment with dithiothreitol, a thiol (-SH) reducing agent, did not reverse the effects of hyperthermia. A variety of global lipoxygenase (LOX) inhibitors further depressed force during 43 degrees C and caused a significant loss of thermal tolerance at 42 degrees C. Cyclooxygenase (COX) inhibitors also caused a loss of thermal tolerance at 42 degrees C. Blockage of phospholipase with phospholipase A(2) inhibitors, bromoenol lactone or arachidonyltrifluoromethyl ketone failed to significantly prevent the loss of force at 43 degrees C. Overall, these data suggest that ROS do not play an apparent role in the loss of contractile function during severe hyperthermia in diaphragm. However, functional LOX and COX enzyme activities appear to be necessary for maintaining normal force production in hyperthermia.
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Affiliation(s)
- S Ryan Oliver
- University of Florida, Department of Applied Physiology and Kinesiology, Gainesville, Florida 32611, USA
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11
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Changes in skeletal muscle expression of AQP1 and AQP4 in dystrophinopathy and dysferlinopathy patients. Acta Neuropathol 2008; 116:235-46. [PMID: 18392839 DOI: 10.1007/s00401-008-0369-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 02/12/2008] [Accepted: 03/13/2008] [Indexed: 10/22/2022]
Abstract
Transmembrane water transport is mediated by aquaporins (AQPs), of which AQP1 and AQP4 are expressed in skeletal muscle. AQP4 expression is reduced in Duchenne muscular dystrophy (DMD) patients, and is reported to correlate with decreased alpha1-syntrophin and altered osmotic permeability. In this study, we assessed the relationship between AQP1, AQP4, dystrophin and alpha1-syntrophin in dystrophinopathy and dysferlinopathy patients. Muscle biopsies of patients with DMD (n = 8) and limb-girdle muscular dystrophy type 2B (LGMD2B; n = 5) were screened for AQP1 and AQP4 expression by real-time quantitative RT-PCR or Western blot and immunohistochemistry. AQP expression was further analyzed in primary myotubes derived from DMD and LGMD2B patients by cell culture and immunohistochemistry. AQP1 transcript and protein expression was significantly elevated in DMD biopsies, and was localized to the sarcolemma of muscle fibers and endothelia of muscle capillaries. AQP4 was significantly reduced despite normal dystrophin and alpha1-syntrophin in dysferlinopathy patients, while expression of AQP1 was variably upregulated. Expression of AQP1 and AQP4 was normal in patient-derived primary myotubes, suggesting that altered AQPs observed in biopsies are likely secondary to the dystrophic process. Our study shows that AQP4 downregulation can occur in muscular dystrophies with either normal or disrupted expression of dystrophin-associated proteins, and that this might be associated with upregulation of AQP1.
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12
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Antolic A, Harrison R, Farlinger C, Cermak NM, Peters SJ, LeBlanc P, Roy BD. Effect of extracellular osmolality on cell volume and resting metabolism in mammalian skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2007; 292:R1994-2000. [PMID: 17234958 DOI: 10.1152/ajpregu.00653.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of the present investigation was to establish an in vitro mammalian skeletal muscle model to study acute alterations in resting skeletal muscle cell volume. Isolated, whole muscles [soleus and extensor digitorum longus (EDL)] were dissected from Long-Evans rats and incubated for 60 min in Sigma medium 199 (1 g of resting tension, bubbled with 95% O2-5% O2, 30 ± 2°C, and pH 7.4). Medium osmolality was altered to simulate hyposmotic (190 ± 10 mmol/kg) or hyperosmotic conditions (400 ± 10 mmol/kg), whereas an isosmotic condition (290 ± 10 mmol/kg) served as a control. After incubation, relative water content of the muscle decreased with hyperosmotic and increased with hyposmotic condition in both muscle types ( P < 0.05). The cross-sectional area of soleus type I and type II fibers increased ( P < 0.05) in hyposmotic, whereas hyperosmotic exposure led to no detectable changes. The EDL type II fiber area decreased in the hyperosmotic condition and increased after hyposmotic exposure, whereas no change was observed in EDL type I fibers. Furthermore, exposure to the hyperosmotic condition in both muscle types resulted in decreased muscle ATP and phosphocreatine ( P < 0.05) contents and increased creatine and lactate contents ( P < 0.05) compared with control and hyposmotic conditions. This isolated skeletal muscle model proved viable and demonstrated that altering extracellular osmolality could cause acute alterations in muscle water content and resting muscle metabolism.
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Affiliation(s)
- AnaMaria Antolic
- Faculty of Applied Health Sciences, Brock Univ, St Catharines, ON, Canada
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13
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Usher-Smith JA, Fraser JA, Huang CLH, Skepper JN. Alterations in triad ultrastructure following repetitive stimulation and intracellular changes associated with exercise in amphibian skeletal muscle. J Muscle Res Cell Motil 2007; 28:19-28. [PMID: 17333488 PMCID: PMC3714558 DOI: 10.1007/s10974-007-9100-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 01/05/2007] [Indexed: 11/06/2022]
Abstract
This study used Rana temporaria sartorius muscles to examine the effect of fatiguing electrical stimulation on the gap between the T-tubular and sarcoplasmic reticular membranes (T-SR distance) and the T-tubule diameter and compared this with corresponding effects on resting fibres exposed to a range of extracellular conditions that each replicate one of the major changes associated with muscular activity: membrane depolarisation, isotonic volume increase, acidification and intracellular lactate accumulation. Following each treatment, muscles were immersed in isotonic fixative solution and processed for transmission electron microscopy (TEM). Mean T-SR distances were estimated from orthogonal intercepts to provide estimates of diffusion distances between T and SR membranes and T-tubule diameter was estimated by measuring its shortest axis in the sampled J-SR complexes. Measurements from muscles fatigued by low frequency intermittent stimulation showed significant (P << 0.05) reversible increases in both T-SR distance and T-tubule diameter from 15.97 ± 0.37 nm to 20.15 ± 0.56 nm and from 15.44 ± 0.60 nm to 22.26 ± 0.84 nm (n = 40, 30) respectively. Exposure to increasing concentrations of extracellular [K+] in the absence of Cl− to produce membrane depolarisation without accompanying cell swelling reduced T-SR distance and increased T-tubule diameter, whilst comparable increases in [K+]e in the presence of Cl− suggested that isotonic cell swelling has the opposite effect. Acidification alone, produced by NH4Cl addition and withdrawal, also decreased T-SR distance and T-tubule diameter. A similar reduction in T-SR distance occurred following exposure to extracellular Na-lactate where such acidification was accompanied by elevations of intracellular lactate, but these conditions produced a significant swelling of T-tubules attributable to movement of lactate from the cell into the T-tubules. This study thus confirms previous reports of significant increases in T-SR distance and T-tubule diameter following stimulation. However, of membrane depolarisation, isotonic cell swelling, intracellular acidification and lactate accumulation, only isotonic cell swelling increases T-SR distance whilst membrane depolarisation and intracellular lactate likely contribute to the observed increases in T-tubule diameter.
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Affiliation(s)
- Juliet A Usher-Smith
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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Usher-Smith JA, Fraser JA, Bailey PSJ, Griffin JL, Huang CLH. The influence of intracellular lactate and H+ on cell volume in amphibian skeletal muscle. J Physiol 2006; 573:799-818. [PMID: 16613877 PMCID: PMC1779748 DOI: 10.1113/jphysiol.2006.108316] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 02/23/2006] [Accepted: 04/11/2006] [Indexed: 12/11/2022] Open
Abstract
The combined effects of intracellular lactate and proton accumulation on cell volume, Vc, were investigated in resting Rana temporaria striated muscle fibres. Intracellular lactate and H+ concentrations were simultaneously increased by exposing resting muscle fibres to extracellular solutions that contained 20-80 mm sodium lactate. Cellular H+ and lactate entry was confirmed using pH-sensitive electrodes and 1H-NMR, respectively, and effects on Vc were measured using confocal microscope xz-scanning. Exposure to extracellular lactate up to 80 mm produced significant changes in pH and intracellular lactate (from a pH of 7.24 +/- 0.03, n = 8, and 4.65 +/- 1.07 mm, n = 6, respectively, in control fibres, to 6.59 +/- 0.03, n = 4, and 26.41 +/- 0.92 mm, n = 3, respectively) that were comparable to those observed following fatiguing stimulation (6.30-6.70 and 18.04 +/- 1.78 mm, n = 6, respectively). Yet, the increase in intracellular osmolarity expected from such an increase in intracellular lactate did not significantly alter Vc. Simulation of these experimental results, modified from the charge difference model of Fraser & Huang, demonstrated that such experimental manoeuvres produced changes in intracellular [H+] and [lactate] comparable to those observed during muscle fatigue, and accounted for this paradoxical conservation of Vc through balancing negative osmotic effects resulting from the net cation efflux that would follow a titration of intracellular membrane-impermeant anions by the intracellular accumulation of protons. It demonstrated that with established physiological values for intracellular buffering capacity and the permeability ratio of lactic acid and anionic lactate, P(LacH): P(Lac-), this would provide a mechanism that precisely balanced any effect on cell volume resulting from lactate accumulation during exercise.
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MESH Headings
- Animals
- Cell Size
- Hydrogen-Ion Concentration
- Intracellular Fluid/chemistry
- Intracellular Fluid/metabolism
- Membrane Potentials
- Microscopy, Confocal
- Models, Biological
- Muscle Fatigue/physiology
- Muscle Fibers, Skeletal/chemistry
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/physiology
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/cytology
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/physiology
- Protons
- Rana temporaria
- Sodium Lactate/metabolism
- Time Factors
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Affiliation(s)
- Juliet A Usher-Smith
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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Usher-Smith JA, Skepper JN, Fraser JA, Huang CLH. Effect of repetitive stimulation on cell volume and its relationship to membrane potential in amphibian skeletal muscle. Pflugers Arch 2006; 452:231-9. [PMID: 16404610 DOI: 10.1007/s00424-005-0022-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 10/31/2005] [Accepted: 11/07/2005] [Indexed: 10/25/2022]
Abstract
The effect of electrical stimulation on cell volume, V (c), and its relationship to membrane potential, E (m), was investigated in Rana temporaria striated muscle. Confocal microscope xz-plane scanning and histology of plastic sections independently demonstrated significant and reversible increases in V (c) of 19.8+/-0.62% (n=3) and 27.1+/-8.62% (n=3), respectively, after a standard stimulation protocol. Microelectrode measurements demonstrated an accompanying membrane potential change, DeltaE (m), of +23.6+/-0.98 mV (n=3). The extent to which this DeltaE (m) might contribute to the observed changes in V (c) was explored in quiescent muscle exposed to variations in extracellular potassium concentration, [K(+)](e). E (m) and V (c) varied linearly with log [K(+)](e) and [K(+)](e), respectively, in the range 2.5-15 mM (R (2)=0.99 and 0.96), and these results were used to reconstruct an approximately linear relationship between V (c) and E (m) (DeltaV (c)=0.85E (m)+68.53; R (2)=0.99) and hence derive the DeltaV (c) expected from the DeltaE (m) during stimulation. This demonstrated that both the time course and magnitude of the increase and recovery of V (c) observed in active muscles could be reproduced by the corresponding [K(+)](e)-induced depolarisation in quiescent muscles, suggesting that the depolarisation associated with membrane activity makes a substantial contribution to the cell swelling during exercise. Furthermore, conditions of Cl(-) deprivation abolished the relationship between E (m) and V (c), supporting a mechanism in which the depolarisation of E (m) drives a passive redistribution of Cl(-) and hence cellular entry of Cl(-) and K(+) and an accompanying, osmotically driven, increase in V (c).
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Affiliation(s)
- Juliet A Usher-Smith
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
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Affiliation(s)
- Michael I Lindinger
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.
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Frigeri A, Nicchia GP, Balena R, Nico B, Svelto M. Aquaporins in skeletal muscle: reassessment of the functional role of aquaporin‐4. FASEB J 2004; 18:905-7. [PMID: 15033928 DOI: 10.1096/fj.03-0987fje] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Aquaporin-4 (AQP4) is the major water channel of the neuromuscular system, but its physiological function in both perivascular astrocytes and skeletal muscle sarcolemma is unclear. The purpose of this study was to assess the following in skeletal muscle: a) the expression of all cloned water cannels; b) the functional role of AQP4 using sarcolemma vesicles purified by means of several fractionation methods, and c) the functional effect of AQP4 reduction in mdx mice, the animal model of Duchenne muscular dystrophy (DMD). Immunofluorescence and immunoblot experiments performed with affinity purified antibodies revealed that only AQP1 and AQP4 are expressed in mouse skeletal muscle: AQP1 in endothelial cells of continuous capillaries and AQP4 on the plasma membrane of muscle fiber. Plasma membrane vesicle purification was performed with a procedure extensively used to purify and characterize dystrophin-associated proteins (DAPs) from rabbit skeletal muscle. Western blot analysis showed strong co-enrichment of the analyzed DAPs and AQP4, indicating that the membrane vesicle preparation was highly enriched in sarcolemma. Stopped-flow light-scattering measurements showed high osmotic water permeability of sarcolemma vesicles (approximately 150 microm/s) compatible with the AQP-mediated pathway for water movement. Sarcolemma vesicles prepared from mdx mice revealed, in parallel with AQP4 disappearance from the plasma membrane, a strong reduction in water permeability compared with wild-type mice. Altogether, these results demonstrate high AQP4-mediated water permeability of the skeletal muscle sarcolemma. Expression of sarcolemmal AQP4 together with that of vascular AQP1 may be responsible for the fast water transfer from the blood into the muscle during intense activity. These data imply an important role for aquaporins in skeletal muscle physiology as well as an involvement of AQP4 in the molecular alterations that occur in the muscle of DMD patients.
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Affiliation(s)
- Antonio Frigeri
- Department of General and Environmental Physiology and Centre of Excellence in Comparative Genomics (CEGBA), University of Bari, Bari, Italy.
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Hoskins BK, Ashley CC, Rapp G, Griffiths PJ. Time-resolved X-ray diffraction by skinned skeletal muscle fibers during activation and shortening. Biophys J 2001; 80:398-414. [PMID: 11159411 PMCID: PMC1301242 DOI: 10.1016/s0006-3495(01)76023-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Force, sarcomere length, and equatorial x-ray reflections (using synchrotron radiation) were studied in chemically skinned bundles of fibers from Rana temporaria sartorius muscle, activated by UV flash photolysis of a new photolabile calcium chelator, NP-EGTA. Experiments were performed with or without compression by 3% dextran at 4 degrees C. Isometric tension developed at a similar rate (t(1/2) = 40 +/- 5 ms) to the development of tetanic tension measured in other studies (Cecchi et al., 1991). Changes in intensity of equatorial reflections (I(11) t(1/2), 15-19 ms; I(10) t(1/2), 24-26 ms) led isometric tension development and were faster than for tetanus. During shortening at 0.14P(o), I(10) and I(11) changes were partially reversed (18% and 30%, respectively, compressed lattice), in agreement with intact cell data. In zero dextran, activation caused a compression of A-band lattice spacing by 0.7 nm. In 3% dextran, activation caused an expansion of 1.4 nm, consistent with an equilibrium spacing of 45 nm. But, in both cases, discharge of isometric tension by shortening caused a rapid lattice expansion of 1.0-1.1 nm, suggesting discharge of a compressive cross-bridge force, with or without compression by dextran, and the development of an additional expansive force during activation. In contrast to I(10) and I(11) data, these findings for lattice spacing did not resemble intact fiber data.
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Affiliation(s)
- B K Hoskins
- University Laboratory of Physiology, Oxford OX1 3PT, United Kingdom
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