Biochemical adaptations in skeletal muscle of trained thyroidectomized rats

1976 ◽  
Vol 230 (5) ◽  
pp. 1194-1197 ◽  
Author(s):  
RL Terjung ◽  
JE Koerner
Keyword(s):  
Skeletal Muscle ◽  
Cytochrome C ◽  
Training Program ◽  
Muscle Fibers ◽  
Oxidative Capacity ◽  
Treadmill Running ◽  
Absolute Increase ◽  
Normal Thyroid Function ◽  
Slow Twitch ◽  
Fast Twitch

The cytochrome c concentrations of the different types of skeletal muscle of trained and nontrained normal and thyroidectomized rats were measured. Animals were trained by treadmill running 1 mph, at a 15% incline, 1 h/day, 5 days/wk for at least 12 wk. This training program induced an expected 50% increase in cytochrome c in the high-oxidative fast-twitch red (FTR) and slow-twitch red (STR) fibers and only a 25% increase in the low-oxidative fast-twitch white (FTW) fibers of the normal rats. This same training program caused a greater increase (100%) in the FTR and STR fibers of the thyroidectomized runners and a dramatic 243% increase in the FTW fiber. Even though the thyroidectomy procedure caused a reduction in oxidative capacity of all types of skeletal muscle fibers to about one-half normal, the absolute increase in cytochrome c in the muscles of the trained thyroidectomized animals was essentially the same or greater than that of the normal trained animals. These results indicate that the adaptive response to training of an increased oxidative capacity in skeletal muscle occurs in the absence of normal thyroid function. They also suggest that the exercise bouts of the thyroidectomized animals were performed with a relatively greater involvement of the FTW muscle fibers.

Na current density at and away from end plates on rat fast- and slow-twitch skeletal muscle fibers

1992 ◽  
Vol 262 (1) ◽  
pp. C229-C234 ◽  
Author(s):  
R. L. Ruff
Keyword(s):  
Skeletal Muscle ◽  
Current Density ◽  
Muscle Fibers ◽  
Postsynaptic Membrane ◽  
Na Current ◽  
End Plate ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

Na current density and membrane capacitance were studied with the loose patch voltage clamp technique on rat fast- and slow-twitch skeletal muscle fibers at three different regions on the fibers: 1) the end plate border, 2) greater than 200 microns from the end plate (extrajunctional), and 3) on the end plate postsynaptic membrane. Fibers were treated with collagenase to improve visualization of the end plate and to enzymatically remove the nerve terminal. The capacitance of membrane patches was similar on fast- and slow-twitch fibers and patches of membrane on the end plate had twice the capacitance of patches elsewhere. For fast- and slow-twitch fibers, the sizes of the Na current normalized to the area of the patch were as follows: end plate greater than end plate border greater than extrajunctional. For both types of fibers, the amplitudes of the Na current normalized to the capacitance of the membrane patch were as follows: end plate approximately end plate border greater than extrajunctional. At each of the three regions, the Na current densities were larger on fast-twitch fibers and fast-twitch fibers had a larger increase in Na current density at the end plate border compared with extrajunctional membrane.

scholarly journals Activity-dependent nuclear translocation and intranuclear distribution of NFATc in adult skeletal muscle fibers

2001 ◽  
Vol 155 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Yewei Liu ◽  
Zoltán Cseresnyés ◽  
William R. Randall ◽  
Martin F. Schneider
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Nuclear Translocation ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Adult Skeletal Muscle ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
Nuclear Foci ◽  
Fast Twitch

TTranscription factor nuclear factor of activated T cells NFATc (NFATc1, NFAT2) may contribute to slow-twitch skeletal muscle fiber type–specific gene expression. Green fluorescence protein (GFP) or FLAG fusion proteins of either wild-type or constitutively active mutant NFATc [NFATc(S→A)] were expressed in cultured adult mouse skeletal muscle fibers from flexor digitorum brevis (predominantly fast-twitch). Unstimulated fibers expressing NFATc(S→A) exhibited a distinct intranuclear pattern of NFATc foci. In unstimulated fibers expressing NFATc–GFP, fluorescence was localized at the sarcomeric z-lines and absent from nuclei. Electrical stimulation using activity patterns typical of slow-twitch muscle, either continuously at 10 Hz or in 5-s trains at 10 Hz every 50 s, caused cyclosporin A–sensitive appearance of fluorescent foci of NFATc–GFP in all nuclei. Fluorescence of nuclear foci increased during the first hour of stimulation and then remained constant during a second hour of stimulation. Kinase inhibitors and ionomycin caused appearance of nuclear foci of NFATc–GFP without electrical stimulation. Nuclear translocation of NFATc–GFP did not occur with either continuous 1 Hz stimulation or with the fast-twitch fiber activity pattern of 0.1-s trains at 50 Hz every 50 s. The stimulation pattern–dependent nuclear translocation of NFATc demonstrated here could thus contribute to fast-twitch to slow-twitch fiber type transformation.

Effect of exercise on lipoprotein lipase activity in rat heart and skeletal muscle

1975 ◽  
Vol 229 (2) ◽  
pp. 394-397 ◽  
Author(s):  
J Borensztajn ◽  
MS Rone ◽  
SP Babirak ◽  
JA McGarr ◽  
LB Oscai
Keyword(s):  
Skeletal Muscle ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Plasma Triglyceride ◽  
Treadmill Running ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Lipoprotein Lipase Activity ◽  
Slow Twitch ◽  
Fast Twitch

Lipoprotein lipase activity was measured in the three skeletal muscle fiber types of untrained rats and in those of rats subjected to a 12-wk program of treadmill running. Lipoprotein lipase activity in slow-twitch red fibers was approximately 14- to 20-fold higher (P less than 0.001) than that in fast-twitch white and approximately 2-fold higher (P less than 0.001) than that in fast-twitch red fibers in the untrained animals. These results suggest that, in sedentary animals, mainly slow-twitch red and fast-twitch red fibers are capable of taking up plasma triglyceride fatty acids. Regularly performed endurance exercise resulted in significant increase (2- to 4.5-fold) in lipoprotein lipase activity in the three muscle fiber types examined. The increase in lipoprotein lipase activity in response to treadmill running suggests that exercise increases the capacity of these fibers to take up and oxidize plasma triglyceride fatty acids. Cardiac muscle did not undergo an exercise-induced increase in the levels of activity of lipoprotein lipase similar to that seen in skeletal muscle.

Skeletal muscle cytochrome c and myoglobin, endurance, and frequency of training

1981 ◽  
Vol 51 (3) ◽  
pp. 746-749 ◽  
Author(s):  
R. C. Hickson
Keyword(s):  
Skeletal Muscle ◽  
Cytochrome C ◽  
Vastus Lateralis ◽  
Training Group ◽  
Treadmill Running ◽  
Female Rats ◽  
Time To Exhaustion ◽  
Training Frequency ◽  
Muscle Types ◽  
Fast Twitch

This study was undertaken to evaluate the effects of various training frequencies on performance capacity, the mitochondrial marker cytochrome c, and myoglobin, which is responsible for storage and transport of O2, in the three types of skeletal muscle. Female rats were trained by treadmill running up to 120 min/day, either 2, 4, or 6 days/wk for 14 wk. As a result of training, exercise time to exhaustion was increased in proportion to the number of training sessions per week. Cytochrome c concentration increased (range 20–90%) as a linear function of the number of exercises per week in the fast-twitch red vastus lateralis (FTR), the slow-twitch soleus (STR), and the mixed plantaris muscles. However, the concentration of cytochrome c in fast-twitch white vastus lateralis (FTW) muscles increased to approximately the same extent (40–50%) in all training groups. The increases in myoglobin concentration (13–45%) with training were significantly related to frequency in FTR muscle but not in STR muscle. Myoglobin levels in FTW muscle remained unchanged, regardless of training group. These results provide evidence that the capacity to perform endurance exercise and the mitochondrial content of the red skeletal muscle types are directly affected by training frequency.

Separate turnover of cytochrome c and myoglobin in the red types of skeletal muscle

1981 ◽  
Vol 241 (3) ◽  
pp. C140-C144 ◽  
Author(s):  
R. C. Hickson ◽  
M. A. Rosenkoetter
Keyword(s):  
Skeletal Muscle ◽  
Cytochrome C ◽  
Time Course ◽  
Base Line ◽  
Turnover Rates ◽  
Fast Red ◽  
Slow Twitch ◽  
Exercise Endurance ◽  
Rate Of Decline ◽  
Fast Twitch

The purpose of this investigation was to determine whether cytochrome c and myoglobin have similar turnover rates in the three types of skeletal muscles. Exercise (endurance training) was used as an inducing stimulus to increase their concentrations. The half-lives (t 1/2) were subsequently estimated from the time course of return to base-line levels after cessation of exercise. When exercise was stopped, cytochrome c concentration returned rapidly to control levels; the lengths of t 1/2 were approximately 8 days in fast-twitch red, 5 days in slow-twitch red, and 9 days in mixed muscles. These findings confirm previous results of cytochrome c turnover. The concentration of myoglobin decreased at a slower rate than that observed for cytochrome c during detraining in fast-red slow-red, and plantaris muscles, and did not return to sedentary control levels throughout the 50-day detraining period. Myoglobin concentration in fast-twitch white muscle did not increase with the training. These results provide evidence that the degradation rate of myoglobin differs from that of cytochrome c in the red types of skeletal muscle. These elevated myoglobin levels may, in part, provide one explanation for the slow rate of decline in aerobic power that has been observed when individuals stop exercising.

scholarly journals A myosin-based mechanism for stretch activation and its possible role revealed by varying phosphate concentration in fast and slow mouse skeletal muscle fibers

2019 ◽  
Vol 317 (6) ◽  
pp. C1143-C1152 ◽  
Author(s):  
Chad R. Straight ◽  
Kaylyn M. Bell ◽  
Jared N. Slosberg ◽  
Mark S. Miller ◽  
Douglas M. Swank
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Muscle Length ◽  
Power Stroke ◽  
Mammalian Skeletal Muscle ◽  
Stretch Activation ◽  
Force Ratio ◽  
Slow Twitch ◽  
Fast Twitch

Stretch activation (SA) is a delayed increase in force following a rapid muscle length increase. SA is best known for its role in asynchronous insect flight muscle, where it has replaced calcium’s typical role of modulating muscle force levels during a contraction cycle. SA also occurs in mammalian skeletal muscle but has previously been thought to be too low in magnitude, relative to calcium-activated (CA) force, to be a significant contributor to force generation during locomotion. To test this supposition, we compared SA and CA force at different Pi concentrations (0–16 mM) in skinned mouse soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscle fibers. CA isometric force decreased similarly in both muscles with increasing Pi, as expected. SA force decreased with Pi in EDL (40%), leaving the SA to CA force ratio relatively constant across Pi concentrations (17–25%). In contrast, SA force increased in soleus (42%), causing a quadrupling of the SA to CA force ratio, from 11% at 0 mM Pi to 43% at 16 mM Pi, showing that SA is a significant force modulator in slow-twitch mammalian fibers. This modulation would be most prominent during prolonged muscle use, which increases Pi concentration and impairs calcium cycling. Based upon our previous Drosophila myosin isoform studies and this work, we propose that in slow-twitch fibers a rapid stretch in the presence of Pi reverses myosin’s power stroke, enabling quick rebinding to actin and enhanced force production, while in fast-twitch fibers, stretch and Pi cause myosin to detach from actin.

scholarly journals Myofibrillar regulatory mechanisms of stretch activation in mammalian striated muscle

2017 ◽  
Author(s):  
◽  
Joel C. Robinett
Keyword(s):  
Skeletal Muscle ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Stretch Activation ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
Low Levels ◽  
Slow Twitch Fibers ◽  
Fast Twitch ◽  
Transient Force

Stretch activation is described as a delayed increase in force after an imposed stretch. This process is essential in the flight muscles of many insects and is also observed, to some degree, in mammalian striated muscles. The mechanistic basis for stretch activation remains uncertain, although it appears to involve cooperative activation of the thin filaments (12, 80). The purpose of this study was to address myofibrillar regulatory mechanisms of stretch activation in mammalian striated muscle. For these studies, permeabilized rat slow-twitch and fast-twitch skeletal muscle fibers were mounted between a force transducer and motor, and a slack-re-stretch maneuver was performed over a range of Ca[superscript 2+] activation levels. Following slack-re-stretch there was a stretch activation process that often resulted in a transient force overshoot (P[subscript TO]), which was quantified relative to steady-state isometric force. P[subscript TO] was highly dependent upon Ca[superscript 2+] activation level, and the relative magnitude of P[subscript TO] was greater in slow-twitch fibers than fast-twitch fibers. In both slow-twitch and fast-twitch fibers, force redevelopment involved a fast, Ca[superscript 2+] activation dependent process (k1) and a slower, less activation dependent process (k2). Interestingly, the two processes converged at low levels of Ca[superscript 2+] activation in both fiber types. P[subscript TO] also contained a relaxation phase, which progressively slowed as Ca[superscript 2+] activation levels increased and was more Ca[superscript 2+] activation dependent in slow-twitch fibers. These results suggest that stretch activation may not be solely regulated by the extent of apparent cooperative activation of force due to a higher relative level of stretch activation in the less cooperative slow-twitch skeletal muscle fiber. Next, we investigated an additional potential molecular mechanism by regulating stretch activation in mammalian striated muscle. Along these lines, our lab has previously observed that PKA-induced phosphorylation of cMyBP-C and cTnI elicited a significant increase in transient force overshoot following slack-re-stretch maneuver in permeabilized cardiac myocytes (29). Interestingly, in slow-twitch skeletal muscle fibers MyBP-C but not ssTnI is phosphorylated by PKA (28). We, thus, took advantage of this variation in substrates phosphorylated by PKA to investigate the effects of PKA-induced phosphorylation of MyBP-C on stretch activation in slow-twitch skeletal muscle fibers. Following PKA treatment of skinned slow-twitch skeletal muscle fibers, the magnitude of P[subscript TO] more than doubled, but this only occurred at low levels of Ca[superscript 2+] activation (i.e., [approximately]25% maximal Ca[superscript 2+] activated force). Also, force redevelopment rates were significantly increased over the entire range of Ca[superscript 2+] activation levels following PKA treatment. In a similar manner, force decay rates showed a tendency of being faster following PKA treatment, however, were only statistically significantly faster at 50% Ca[superscript 2+] activation. Overall, these results are consistent with a model whereby stretch transiently increases the number of cross-bridges made available for force generation and PKA phosphorylation of MyBP-C enhances these stretch activation processes.

Ammonia and IMP in different skeletal muscle fibers after exercise in rats

1980 ◽  
Vol 49 (6) ◽  
pp. 1037-1041 ◽  
Author(s):  
R. A. Meyer ◽  
G. A. Dudley ◽  
R. L. Terjung
Keyword(s):  
Skeletal Muscle ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Treadmill Running ◽  
Strenuous Exercise ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Glycolytic Intermediate ◽  
Lactate Levels ◽  
Fast Twitch

Adenosine 5'-monophosphate (AMP) deamination, estimated from inosine 5'-monophosphate (IMP) accumulation, was studied in the different skeletal muscle fiber types of untrained rats anesthetized with ether immediately after 4 min of treadmill running at 45 or 60 m/min. The adenylosuccinate synthetase-inhibitor hadacidin was administered (200 mg/kg ip) before exercise to block IMP reamination and, therefore, to provide a better assessment of IMP formation. The increases in blood ammonia after exercise (2.5- and 5-fold, respectively) were highly correlated (r = 0.93) with the increases in blood lactate levels (6- and 11-fold). At both speeds, IMP increased in fast-twitch but not in slow-twitch (soleus) muscle. Of the fast muscles, the increase in IMP was greatest (up to 4 mumol/g wet wt) in the white vastus lateralis (fast twitch, glycolytic), intermediate in the plantaris (mixed fibers), and lowest in the red vastus lateralis (fast twitch, oxidative glycolytic). The increases in IMP were coincident with nearly equivalent decreases in ATP. Hadacidin treatment resulted in a greater IMP accumulation after exercise in both fast-twitch types but not in the soleus. The results indicate that fast-twitch muscle fibers, particularly the fast-twitch glycolytic fibers, are the source of the ammonia produced during strenuous exercise.

Glycogenesis and glyconeogenesis in skeletal muscle: effects of pH and hormones

1990 ◽  
Vol 258 (4) ◽  
pp. E693-E700 ◽  
Author(s):  
A. Bonen ◽  
J. C. McDermott ◽  
M. H. Tan
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Extensor Digitorum Longus ◽  
Muscle Fibers ◽  
Extensor Digitorum ◽  
Effects Of Ph ◽  
Slow Twitch ◽  
Highly Correlated ◽  
Fast Twitch

We examined the effects of selected hormones and pH on the rates of glyconeogenesis (L-[U-14C]-lactate----glycogen) and glycogenesis (D-[U-14C]glucose----glycogen) in mouse fast-twitch (FT) and slow-twitch muscles incubated in vitro (37 degrees C). Glyconeogenesis and glycogenesis increased linearly with increasing concentrations of lactate (5-20 mM) and glucose (2.5-10 mM), respectively, in both muscles. Glyconeogenesis was approximately three- to fourfold greater in the extensor digitorum longus (EDL) than in the soleus, whereas basal glycogenesis was twofold greater in the soleus muscle than in the EDL. Lactate accounted for up to 5% of the glycogen formed in the soleus and up to 32% in the EDL relative to the rates of glycogenesis (i.e., 5 mM glucose + 10 nM insulin) in each muscle. Corticosterone (10(-12)-10(-6) M) failed to alter glyconeogenesis, whereas this hormone reduced glycogenesis. Insulin (10 nM) markedly stimulated glycogenesis but failed to stimulate glyconeogenesis. The rates of both glycogenesis and glyconeogenesis were pH sensitive, with optimal rates at pH 6.5-7.0 in both muscles. Glyconeogenesis increased by 49% in the soleus and by 39% EDL at pH 6.5 compared with pH 7.4. Glycogenesis increased in the soleus (SOL) and EDL in the absence (SOL: +22%; EDL: +52%) and presence of insulin (SOL: +22%; EDL: +51%) at pH 6.5 when compared with pH 7.4. In additional experiments with the perfused rat hindquarter, rates of glyconeogenesis were shown to be highly correlated with proportion of FT muscle fibers in a muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of PGC-1α on control of microvascular Po2 kinetics following onset of muscle contractions

2014 ◽  
Vol 117 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Yutaka Kano ◽  
Shinji Miura ◽  
Hiroaki Eshima ◽  
Osamu Ezaki ◽  
David C. Poole
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Endurance Performance ◽  
Oxidative Capacity ◽  
Muscle Contractions ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Phosphorescence Quenching ◽  
Slow Twitch ◽  
Fast Twitch

During contractions, regulation of microvascular oxygen partial pressure (Pmvo2), which drives blood-myocyte O2 flux, is a function of skeletal muscle fiber type and oxidative capacity and can be altered by exercise training. The kinetics of Pmvo2 during contractions in predominantly fast-twitch muscles evinces a more rapid fall to far lower levels compared with slow-twitch counterparts. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) improves endurance performance, in part, due to mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. We tested the hypothesis that improvement of exercise capacity by genetic overexpression of PGC-1α would be associated with an altered Pmvo2 kinetics profile of the fast-twitch (white) gastrocnemius during contractions toward that seen in slow-twitch muscles (i.e., slowed response kinetics and elevated steady-state Pmvo2). Phosphorescence quenching techniques were used to measure Pmvo2 at rest and during separate bouts of twitch (1 Hz) and tetanic (100 Hz) contractions in gastrocnemius muscles of mice with overexpression of PGC-1α and wild-type littermates (WT) mice under isoflurane anesthesia. Muscles of PGC-1α mice exhibited less fatigue than WT ( P < 0.01). However, except for the Pmvo2 response immediately following onset of contractions, WT and PGC-1α mice demonstrated similar Pmvo2 kinetics. Specifically, the time delay of the Pmvo2 response was shortened in PGC-1α mice compared with WT (1 Hz: WT, 6.6 ± 2.4 s; PGC-1α, 2.9 ± 0.8 s; 100 Hz: WT, 3.3 ± 1.1 s, PGC-1α, 0.9 ± 0.3 s, both P < 0.05). The ratio of muscle force to Pmvo2 was higher for the duration of tetanic contractions in PGC-1α mice. Slower dynamics and maintenance of higher Pmvo2 following muscle contractions is not obligatory for improved fatigue resistance in fast-twitch muscle of PGC-1α mice. Moreover, overexpression of PGC-1α may accelerate O2 utilization kinetics to a greater extent than O2 delivery kinetics.

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