Effects of unweighting and clenbuterol on myosin light and heavy chains in fast and slow muscles of rat

2000 ◽  
Vol 279 (5) ◽  
pp. C1558-C1563 ◽  
Author(s):  
Laurence Stevens ◽  
Carole Firinga ◽  
Bärbel Gohlsch ◽  
Bruno Bastide ◽  
Yvonne Mounier ◽  
...  
Keyword(s):  
Light Chain ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Hindlimb Suspension ◽  
Adrenergic Agonist ◽  
Heavy Chains ◽  
Fast And Slow Muscles ◽  
Induced Changes ◽  
Fast Muscles ◽  
Slow And Fast Muscles

To investigate the plasticity of slow and fast muscles undergoing slow-to-fast transition, rat soleus (SOL), gastrocnemius (GAS), and extensor digitorum longus (EDL) muscles were exposed for 14 days to 1) unweighting by hindlimb suspension (HU), or 2) treatment with the β2-adrenergic agonist clenbuterol (CB), or 3) a combination of both (HU-CB). In general, HU elicited atrophy, CB induced hypertrophy, and HU-CB partially counteracted the HU-induced atrophy. Analyses of myosin heavy (MHC) and light chain (MLC) isoforms revealed HU- and CB-induced slow-to-fast transitions in SOL (increases of MHCIIa with small amounts of MHCIId and MHCIIb) and the upregulation of the slow MHCIa isoform. The HU- and CB-induced changes in GAS consisted of increases in MHCIId and MHCIIb (“fast-to-faster transitions”). Changes in the MLC composition of SOL and GAS consisted of slow-to-fast transitions and mainly encompassed an exchange of MLC1s with MLC1f. In addition, MLC3f was elevated whenever MHCIId and MHCIIb isoforms were increased. Because the EDL is predominantly composed of type IID and IIB fibers, HU, CB, and HU-CB had no significant effect on the MHC and MLC patterns.

scholarly journals Resting membrane potential and Na+,K+-ATPase of rat fast and slow muscles during modeling of hypogravity

2009 ◽  
pp. 599-603 ◽  
Author(s):  
O Tyapkina ◽  
E Volkov ◽  
L Nurullin ◽  
B Shenkman ◽  
I Kozlovskaya ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
The Other ◽  
Hindlimb Suspension ◽  
Resting Membrane Potential ◽  
Sodium Permeability ◽  
Fast And Slow Muscles ◽  
Edl Muscle

Antiorthostatic hindlimb suspension (unloading) decreased the resting membrane potential (RMP) of skeletal muscle fibers in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle of the rat by about 10 % within 7 days and more. Inactivation of the membrane Na+, K+-pump by ouabain brought about similar depolarization as unloading. The increased sodium permeability of the membrane was excluded as the major cause of this depolarization by experiments in which TRIS was substituted for Na+ in the medium. On the other hand, the decrease in the electrogenic participation of the Na+,K+-pump is apparently one of the causes of RMP decrease during hypogravity, in EDL muscle in particular.

Spaceflight on STS-48 and earth-based unweighting produce similar effects on skeletal muscle of young rats

1993 ◽  
Vol 74 (5) ◽  
pp. 2161-2165 ◽  
Author(s):  
M. E. Tischler ◽  
E. J. Henriksen ◽  
K. A. Munoz ◽  
C. S. Stump ◽  
C. R. Woodman ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Space Shuttle ◽  
Weight Bearing ◽  
Similar Rate ◽  
Extensor Digitorum ◽  
Hindlimb Suspension ◽  
Albino Rats ◽  
Sprague Dawley ◽  
Ambient Temperatures

Our knowledge of the effects of unweighting on skeletal muscle of juvenile rapidly growing rats has been obtained entirely by using hindlimb-suspension models. No spaceflight data on juvenile animals are available to validate these models of simulated weightlessness. Therefore, eight 26-day-old female Sprague-Dawley albino rats were exposed to 5.4 days of weightlessness aboard the space shuttle Discovery (mission STS-48, September 1991). An asynchronous ground control experiment mimicked the flight cage condition, ambient shuttle temperatures, and mission duration for a second group of rats. A third group of animals underwent hindlimb suspension for 5.4 days at ambient temperatures. Although all groups consumed food at a similar rate, flight animals gained a greater percentage of body mass per day (P < 0.05). Mass and protein data showed weight-bearing hindlimb muscles were most affected, with atrophy of the soleus and reduced growth of the plantaris and gastrocnemius in both the flight and suspended animals. In contrast, the non-weight-bearing extensor digitorum longus and tibialis anterior muscles grew normally. Earlier suspension studies showed that the soleus develops an increased sensitivity to insulin during unweighting atrophy, particularly for the uptake of 2-[1,2–3H]deoxyglucose. Therefore, this characteristic was studied in isolated muscles within 2 h after cessation of spaceflight or suspension. Insulin increased uptake 2.5- and 2.7-fold in soleus of flight and suspended animals, respectively, whereas it increased only 1.6-fold in control animals. In contrast, the effect of insulin was similar among the three groups for the extensor digitorum longus, which provides a control for potential systemic differences in the animals.

scholarly journals The influence of passive stretch on the growth and protein turnover of the denervated extensor digitorum longus muscle

1978 ◽  
Vol 174 (2) ◽  
pp. 595-602 ◽  
Author(s):  
David F. Goldspink
Keyword(s):  
Protein Synthesis ◽  
Extensor Digitorum Longus ◽  
Similar Rate ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Denervated Muscle ◽  
Longus Muscle ◽  
Induced Changes ◽  
Passive Stretch

At 7 days after cutting the sciatic nerve, the extensor digitorum longus muscle was smaller and contained less protein than its innervated control. Correlating with these changes was the finding of elevated rates of protein degradation (measured in vitro) in the denervated tissue. However, at this time, rates of protein synthesis (measured in vitro) and nucleic acid concentrations were also higher in the denervated tissue, changes more usually associated with an active muscle rather than a disused one. These anabolic trends have, at least in part, been explained by the possible greater exposure of the denervated extensor digitorum longus to passive stretch. When immobilized under a maintained influence of stretch the denervated muscle grew to a greater extent. Although this stretch-induced growth appeared to occur predominantly through a stimulation of protein synthesis, it was opposed by smaller increases in degradative rates. Nucleic acids increased at a similar rate to the increase in muscle mass when a continuous influence of stretch was imposed on the denervated tissue. In contrast, immobilization of the denervated extensor digitorum longus in a shortened unstretched state reversed most of the stretch-induced changes; that is, the muscle became even smaller, with protein synthesis decreasing to a greater extent than breakdown after the removal of passive stretch. The present investigation suggests that stretch will promote protein synthesis and hence growth of the extensor digitorum longus even in the absence of an intact nerve supply. However, some factor(s), in addition to passive stretch, must contribute to the anabolic trends in this denervated muscle.

Myosin light chain phosphorylation-dephosphorylation in mammalian skeletal muscle

1982 ◽  
Vol 242 (3) ◽  
pp. C234-C241 ◽  
Author(s):  
D. R. Manning ◽  
J. T. Stull
Keyword(s):  
Skeletal Muscle ◽  
Light Chain ◽  
Extensor Digitorum Longus ◽  
Myosin Light Chain ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Mammalian Skeletal Muscle ◽  
Phosphate Content ◽  
Longus Muscle ◽  
Fast Twitch

Phosphorylation of the myosin light chain 2 (LC2) subunit was examined in rat fast-twitch and slow-twitch skeletal muscles in response to repetitive stimulation at 23 and 35 degrees C and on incubation of fast-twitch skeletal muscle with isoproterenol. After a 1-s tetany at 35 degrees C, LC2 phosphate content in extensor digitorum longus muscle increased rapidly and transiently from 0.21 to 0.51 mol phosphate/mol LC2. This pattern of phosphorylation was similar to that observed at 23 degrees C. Increases in LC2 phosphate content were dependent on the frequency and duration of stimulation. In soleus muscle LC2 phosphate content was minimal following a 1-s tetany but increased markedly following more prolonged tetanies. On incubation of extensor digitorum longus muscle with isoproterenol (20 microM), LC2 phosphate content did not change, whereas phosphorylase a levels increased. A positive correlation existed between LC2 phosphate content and potentiation of peak twitch tension in both types of muscles, suggesting a physiological function for LC2 phosphorylation.

scholarly journals Chronic hindlimb suspension unloading markedly decreases turnover rates of skeletal and cardiac muscle proteins and adipose tissue triglycerides

2015 ◽  
Vol 119 (1) ◽  
pp. 16-26 ◽  
Author(s):  
Ilya R. Bederman ◽  
Nicola Lai ◽  
Jeffrey Shuster ◽  
Leigh Henderson ◽  
Steven Ewart ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Energy Balance ◽  
Energy Expenditure ◽  
Cardiac Muscle ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Hindlimb Suspension ◽  
Muscle Proteins ◽  
Turnover Rates ◽  
Cardiac Muscles

We previously showed that a single bolus of “doubly-labeled” water (2H218O) can be used to simultaneously determine energy expenditure and turnover rates (synthesis and degradation) of tissue-specific lipids and proteins by modeling labeling patterns of protein-bound alanine and triglyceride-bound glycerol (Bederman IR, Dufner DA, Alexander JC, Previs SF. Am J Physiol Endocrinol Metab 290: E1048–E1056, 2006). Using this novel method, we quantified changes in the whole body and tissue-specific energy balance in a rat model of simulated “microgravity” induced by hindlimb suspension unloading (HSU). After chronic HSU (3 wk), rats exhibited marked atrophy of skeletal and cardiac muscles and significant decrease in adipose tissue mass. For example, soleus muscle mass progressively decreased 11, 43, and 52%. We found similar energy expenditure between control (90 ± 3 kcal·kg−1·day−1) and hindlimb suspended (81 ± 6 kcal/kg day) animals. By comparing food intake (∼112 kcal·kg−1·day−1) and expenditure, we found that animals maintained positive calorie balance proportional to their body weight. From multicompartmental fitting of 2H-labeling patterns, we found significantly ( P < 0.005) decreased rates of synthesis (percent decrease from control: cardiac, 25.5%; soleus, 70.3%; extensor digitorum longus, 44.9%; gastrocnemius, 52.5%; and adipose tissue, 39.5%) and rates of degradation (muscles: cardiac, 9.7%; soleus, 52.0%; extensor digitorum longus, 27.8%; gastrocnemius, 37.4%; and adipose tissue, 50.2%). Overall, HSU affected growth of young rats by decreasing the turnover rates of proteins in skeletal and cardiac muscles and adipose tissue triglycerides. Specifically, we found that synthesis rates of skeletal and cardiac muscle proteins were affected to a much greater degree compared with the decrease in degradation rates, resulting in large negative balance and significant tissue loss. In contrast, we found a small decrease in adipose tissue triglyceride synthesis paired with a large decrease in degradation, resulting in smaller negative energy balance and loss of fat mass. We conclude that HSU in rats differentially affects turnover of muscle proteins vs. adipose tissue triglycerides.

Effects of stretch on work from fast and slow muscles of mice: damped and undamped energy release

2002 ◽  
Vol 80 (9) ◽  
pp. 887-900 ◽  
Author(s):  
Douglas A Syme ◽  
Michael J Grattan
Keyword(s):  
Energy Release ◽  
Extensor Digitorum Longus ◽  
Fibre Length ◽  
Extensor Digitorum ◽  
Total Work ◽  
Active Muscle ◽  
Series Compliance ◽  
Cross Bridges ◽  
Work Done ◽  
Fast Muscles

Stretching active muscle increases the work performed during subsequent shortening. The effects of a preceding stretch on work done by the undamped or lightly damped series compliance (SC) and by the contractile component (CC), which includes cross bridges and damped elements, were assessed using mouse soleus (slow) and extensor digitorum longus (fast) muscles with limited tendon. Increasing stretch amplitude (0–10% fibre length) increased work done by the SC up to a limit, but did not effect work done by the CC. Increasing stretch velocity (10–100% Vmax) had almost no effect on work done by either component. Increasing the delay between the end of stretch and onset of shortening (0–60 ms) caused a decrease in SC work, with no effect on CC work. Recoil of the SC was responsible for 50–70% of the total work done during shortening after stretch. Usually only 10–40% of the energy imparted during the stretch was recovered as work during subsequent shortening; large stretches and long delays between stretch and shortening further reduced this recovery by one third to one fifth. Results are interpreted in the context of a loss of energy stored in the SC owing to forcible detachment of cross bridges with large stretches and cyclic detachment with long delays.Key words: compliance, stretch, work, muscle, undamped.

Ciliary neurotrophic factor prevents unweighting-induced functional changes in rat soleus muscle

2000 ◽  
Vol 88 (5) ◽  
pp. 1623-1630 ◽  
Author(s):  
B. Fraysse ◽  
C. Guillet ◽  
C. Huchet-Cadiou ◽  
D. Conte Camerino ◽  
H. Gascan ◽  
...  
Keyword(s):  
Neurotrophic Factor ◽  
Extensor Digitorum Longus ◽  
Ciliary Neurotrophic Factor ◽  
Extensor Digitorum ◽  
Hindlimb Suspension ◽  
Normal Muscle ◽  
Functional Changes ◽  
Time To Peak ◽  
Pump Flow Rate ◽  
Rat Soleus Muscle

The purpose of the present work was to see whether changes in rat soleus characteristics due to 3 wk of hindlimb suspension could be modified by ciliary neurotrophic factor (CNTF) treatment. Throughout the tail suspension period, the cytokine was delivered by means of an osmotic pump (flow rate 16 μg ⋅ kg−1 ⋅ h−1) implanted under the hindlimb skin. In contrast to extensor digitorum longus, CNTF treatment was able to reduce unweighting-induced atrophy in the soleus. Twitch and 146 mM potassium (K) tensions, measured in small bundles of unloaded soleus, decreased by 48 and 40%, respectively. Moreover, the time to peak tension and the time constant of relaxation of the twitch were 48 and 54% faster, respectively, in unloaded soleus than in normal muscle. On the contrary, twitch and 146 mM K contracture generated in CNTF-treated unloaded and normal soleus were not different. CNTF receptor-α mRNA expression increased in extensor digitorum longus and soleus unloaded nontreated muscles but was similar in CNTF-treated unloaded muscles. The present results demonstrate that exogenously provided CNTF could prevent functional changes occurring in soleus innervated muscle subject to unweighting.

Profiles of connectin (titin) in atrophied soleus muscle induced by unloading of rats

2003 ◽  
Vol 94 (3) ◽  
pp. 897-902 ◽  
Author(s):  
Katsumasa Goto ◽  
Ryoko Okuyama ◽  
Masanori Honda ◽  
Hiroshi Uchida ◽  
Tatsuo Akema ◽  
...  
Keyword(s):  
Extensor Digitorum Longus ◽  
Contractile Function ◽  
Muscle Fibers ◽  
Extensor Digitorum ◽  
Hindlimb Suspension ◽  
Molecular Weights ◽  
Band Region ◽  
Wet Weight ◽  
Fast Twitch ◽  
Significant Increment

Responses of the properties of connectin molecules in the slow-twitch soleus (Sol) and fast-twitch extensor digitorum longus muscles of rats to 3 days of unloading with or without 3-day reloading were investigated. The wet weight (relative to body wt) of Sol, not of extensor digitorum longus, in the unloaded group was significantly less than in the age-matched control ( P < 0.05). Immunoelectron microscopic analyses showed that a monoclonal antibody against connectin (SM1) bound to the I-band region close to the edge of the A band at resting length and moved reversibly away from the Z line as the muscle fibers were stretched. In Sol, the displacement of the SM1-bound dense spots in response to stretching decreased after hindlimb suspension. There were no changes in the molecular weights and the percent distributions of α- and β-connectin in both muscles after hindlimb suspension. A significant increment of percent β-connectin in Sol was observed after 3 days of reloading after hindlimb suspension ( P < 0.05). It is suggested that the elasticity of connectin filaments in the I-band region of the atrophied Sol fibers was reduced relative to that of the control fibers. The lack of the elasticity in atrophied muscle fibers may cause a decrease in contractile function.

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