Hindlimb Unloading Induces a Biphasic Temporal Response of Bcl‐2 Apoptotic Signaling in the Rat Soleus Muscle

This study focuses on the effects of mechanical unloading of rat soleus muscle on the isoform patterns of the three troponin (Tn) subunits: troponin T (TnT), troponin I (TnI), and troponin C (TnC). Mechanical unloading was achieved by hindlimb unloading (HU) for time periods of 7, 15, and 28 days. Relative concentrations of slow and fast TnT, TnI, and TnC isoforms were assessed by electrophoretic and immunoblot analyses. HU induced profound slow-to-fast isoform transitions of all Tn subunits, although to different extents and with different time courses. The effectiveness of the isoform transitions was higher for TnT than for TnI and TnC. Indeed, TnI and TnC encompassed minor partial exchanges of slow isoforms with their fast counterparts, whereas the expression pattern of fast TnT isoforms (TnTf) was largely increased after HU. Moreover, slow and fast isoforms of the different Tn were not affected in the same manner by HU. This suggests that the slow and fast counterparts of the Tn subunit isoforms are regulated independently in response to HU. The changes in TnTf composition occurred in parallel with previously demonstrated transitions within the pattern of the fast myosin heavy chains in the same muscles.

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Adaptation of rat soleus muscle spindles after 21 days of hindlimb unloading

Experimental Neurology ◽

10.1016/j.expneurol.2006.02.003 ◽

2006 ◽

Vol 200 (1) ◽

pp. 191-199 ◽

Cited By ~ 6

Author(s):

C. Rosant ◽

M.D. Nagel ◽

C. Pérot

Keyword(s):

Soleus Muscle ◽

Muscle Spindles ◽

Hindlimb Unloading ◽

Rat Soleus Muscle

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Preventive effect of nucleoprotein on hindlimb unloading-induced capillary regression in rat soleus muscle

Biotechnic & Histochemistry ◽

10.3109/10520295.2013.835444 ◽

2013 ◽

Vol 89 (3) ◽

pp. 220-227 ◽

Cited By ~ 2

Author(s):

Y Kanazawa ◽

K Maekawa ◽

Y Okumura ◽

N Fujita ◽

H Fujino

Keyword(s):

Soleus Muscle ◽

Hindlimb Unloading ◽

Preventive Effect ◽

Rat Soleus Muscle

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The Effect of β-GPA on the Markers of Anabolic and Catabolic Signaling Pathways in Rat Soleus Muscle at the Initial Stage of Hindlimb Unloading

Biochemistry (Moscow) Supplement Series A Membrane and Cell Biology ◽

10.1134/s1990747819060102 ◽

2020 ◽

Vol 14 (1) ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

N. A. Vilchinskaya ◽

E. P. Mochalova ◽

I. I. Paramonova ◽

S. P. Belova ◽

T. M. Mirzoev ◽

...

Keyword(s):

Signaling Pathways ◽

Soleus Muscle ◽

Hindlimb Unloading ◽

Initial Stage ◽

Rat Soleus Muscle

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Key Markers of mTORC1-Dependent and mTORC1-Independent Signaling Pathways Regulating Protein Synthesis in Rat Soleus Muscle During Early Stages of Hindlimb Unloading

Cellular Physiology and Biochemistry ◽

10.1159/000447808 ◽

2016 ◽

Vol 39 (3) ◽

pp. 1011-1020 ◽

Cited By ~ 36

Author(s):

Timur Mirzoev ◽

Sergey Tyganov ◽

Natalia Vilchinskaya ◽

Yulia Lomonosova ◽

Boris Shenkman

Keyword(s):

Protein Synthesis ◽

Signaling Pathways ◽

Soleus Muscle ◽

Ribosome Biogenesis ◽

Hindlimb Unloading ◽

Hindlimb Suspension ◽

28S Rrna ◽

Early Stages ◽

Global Rate ◽

Rat Soleus Muscle

Background/Aims: The purpose of the study was to assess the amount of rRNA and phosphorylation status of the key markers of mTORC1-dependent (70s6k, 4E-BP1) and mTORC1-independent (GSK-3β, AMPK) signaling pathways controlling protein synthesis in rat soleus during early stages of mechanical unloading (hindlimb suspension (HS) for 1-, 3- and 7 days). Methods: The content of the key signaling molecules of various anabolic signaling pathways was determined by Western-blotting. The amount of 28S rRNA was evaluated by RT-PCR. The rate of protein synthesis was assessed using in-vivo SUnSET technique. Results: HS for 3 and 7 days induced a significant (p<0.05) decrease in the rate of global protein synthesis in soleus muscle in comparison with control. HS within 24 hours resulted in a significant (p<0.05) decrease in p-4E-BP1 content, p-AMPK content and increase in p-p70s6k content in rat soleus muscle. Following three days of HS the content of p-AKT was decreased (p<0.05). After 7 days of HS the phosphorylation level of AKT and GSK-3beta was significantly reduced (p<0.05) compared to control. We also observed a significant decrease in the amount of 28S rRNA in rat soleus following 1, 3 and 7 days of HS. Conclusion: Taken together, the results of our study suggest that a decline in the global rate of protein synthesis in rat soleus during early stages of simulated microgravity is associated with impaired ribosome biogenesis as well as reduced activity of mTORC1-independent signaling pathways.

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Ontogenetic, gravity-dependent development of rat soleus muscle

AJP Cell Physiology ◽

10.1152/ajpcell.2001.280.4.c1008 ◽

2001 ◽

Vol 280 (4) ◽

pp. C1008-C1016 ◽

Cited By ~ 38

Author(s):

Yoshinobu Ohira ◽

Takato Tanaka ◽

Tomoo Yoshinaga ◽

Fuminori Kawano ◽

Takeshi Nomura ◽

...

Keyword(s):

Soleus Muscle ◽

Weight Bearing ◽

Postnatal Period ◽

Hindlimb Unloading ◽

Full Weight Bearing ◽

Type I ◽

Myosin Isoforms ◽

Normal Transition ◽

Postural Muscle ◽

Rat Soleus Muscle

We tested the hypothesis that rat soleus muscle fiber growth and changes in myosin phenotype during the postnatal, preweaning period would be largely independent of weight bearing. The hindlimbs of one group of pups were unloaded intermittently from postnatal day 4 to day 21: the pups were isolated from the dam for 5 h during unloading and returned for nursing for 1 h. Control pups were either maintained with the dam as normal or put on an alternating feeding schedule as described above. The enlargement of mass (∼3 times), increase in myonuclear number (∼1.6 times) and myonuclear domain (∼2.6 times), and transformation toward a slow fiber phenotype (from 56 to 70% fibers expressing type I myosin heavy chain) observed in controls were inhibited by hindlimb unloading. These properties were normalized to control levels or higher within 1 mo of reambulation beginning immediately after the unloading period. Therefore, chronic unloading essentially stopped the ontogenetic developmental processes of 1) net increase in DNA available for transcription, 2) increase in amount of cytoplasm sustained by that DNA pool, and 3) normal transition of myosin isoforms that occur in some fibers from birth to weaning. It is concluded that normal ontogenetic development of a postural muscle is highly dependent on the gravitational environment even during the early postnatal period, when full weight-bearing activity is not routine.

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