Temporal responses of oxidative vs. glycolytic skeletal muscles to K+ deprivation: Na+ pumps and cell cations

1999 ◽  
Vol 276 (6) ◽  
pp. C1411-C1419 ◽  
Author(s):  
Curtis B. Thompson ◽  
Cheolsoo Choi ◽  
Jang H. Youn ◽  
Alicia A. McDonough
Keyword(s):  
Skeletal Muscle ◽  
Posttranscriptional Regulation ◽  
Skeletal Muscles ◽  
Extracellular Fluid ◽  
Protein Levels ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Low K ◽  
Muscle Specificity ◽  
White Gastrocnemius

When K+ output exceeds input, skeletal muscle releases intracellular fluid K+ to buffer the fall in extracellular fluid (ECF) K+. To investigate the mechanisms and muscle specificity of the K+ shift, rats were fed K+-deficient chow for 2–10 days, and two muscles at phenotypic extremes were studied: slow-twitch oxidative soleus and fast-twitch glycolytic white gastrocnemius (WG). After 2 days of low-K+ chow, plasma K+ concentration ([K+]) fell from 4.6 to 3.7 mM, and Na+-K+-ATPase α2 (not α1) protein levels in both muscles, measured by immunoblotting, decreased 36%. Cell [K+] decreased from 116 to 106 mM in soleus and insignificantly in WG, indicating that α2 can decrease before cell [K+]. After 5 days, there were further decreases in α2 (70%) and β2 (22%) in WG, not in soleus, whereas cell [K+] decreased and cell [Na+] increased by 10 mM in both muscles. By 10 days, plasma [K+] fell to 2.9 mM, with further decreases in WG α2 (94%) and β2 (70%); cell [K+] fell 19 mM in soleus and 24 mM in WG compared with the control, and cell [Na+] increased 9 mM in soleus and 15 mM in WG; total homogenate Na+-K+-ATPase activity decreased 19% in WG and insignificantly in soleus. Levels of α2, β1, and β2 mRNA were unchanged over 10 days. The ratios of α2 to α1 protein levels in both control muscles were found to be nearly 1 by using the relative changes in α-isoforms vs. β1- (soleus) or β2-isoforms (WG). We conclude that the patterns of regulation of Na+ pump isoforms in oxidative and glycolytic muscles during K+ deprivation mediated by posttranscriptional regulation of α2β1 and α2β2 are distinct and that decreases in α2-isoform pools can occur early enough in both muscles to account for the shift of K+ to the ECF.

Glutamine synthetase induction by glucocorticoids is preserved in skeletal muscle of aged rats

1996 ◽  
Vol 271 (6) ◽  
pp. E1061-E1066 ◽  
Author(s):  
D. Meynial-Denis ◽  
M. Mignon ◽  
A. Miri ◽  
J. Imbert ◽  
E. Aurousseau ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glutamine Synthetase ◽  
Skeletal Muscles ◽  
Female Rats ◽  
Mrna Levels ◽  
Aged Rats ◽  
Adult Rats ◽  
Adult Age ◽  
Slow Twitch ◽  
Fast Twitch

Glutamine synthetase (GS) is a glucocorticoid-inducible enzyme that has a key role for glutamine synthesis in muscle. We hypothesized that the glucocorticoid induction of GS could be altered in aged rats, because alterations in the responsiveness of some genes to glucocorticoids were reported in aging. We compared the glucocorticoid-induced GS in fast-twitch and slow-twitch skeletal muscles (tibialis anterior and soleus, respectively) and heart from adult (age 6-8 mo) and aged (age 22 mo) female rats. All animals received dexamethasone (Dex) in their drinking water (0.77 +/- 0.10 and 0.80 +/- 0.08 mg/day per adult and aged rat, respectively) for 5 days. Dex caused an increase in both GS activity and GS mRNA in fast-twitch and slow-twitch skeletal muscles from adult and aged rats. In contrast, Dex increased GS activity in heart of adult rats, without any concomitant change in GS mRNA levels. Furthermore, Dex did not affect GS activity in aged heart. Thus the responsiveness of GS to an excess of glucocorticoids is preserved in skeletal muscle but not in heart from aged animals.

Phorbol esters affect skeletal muscle glucose transport in a fiber type-specific manner

2004 ◽  
Vol 287 (2) ◽  
pp. E305-E309 ◽  
Author(s):  
David C. Wright ◽  
Paige C. Geiger ◽  
Mark J. Rheinheimer ◽  
Dong Ho Han ◽  
John O. Holloszy
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Glucose Transport ◽  
Soleus Muscle ◽  
Insulin Signaling ◽  
Skeletal Muscles ◽  
Phorbol Esters ◽  
Serine Phosphorylation ◽  
Slow Twitch ◽  
Fast Twitch

Recent evidence has shown that activation of lipid-sensitive protein kinase C (PKC) isoforms leads to skeletal muscle insulin resistance. However, earlier studies demonstrated that phorbol esters increase glucose transport in skeletal muscle. The purpose of the present study was to try to resolve this discrepancy. Treatment with the phorbol ester 12-deoxyphorbol-13-phenylacetate 20-acetate (dPPA) led to an ∼3.5-fold increase in glucose transport in isolated fast-twitch epitrochlearis and flexor digitorum brevis muscles. Phorbol ester treatment was additive to a maximally effective concentration of insulin in fast-twitch skeletal muscles. Treatment with dPPA did not affect insulin signaling in the epitrochlearis. In contrast, phorbol esters had no effect on basal glucose transport and inhibited maximally insulin-stimulated glucose transport ∼50% in isolated slow-twitch soleus muscle. Furthermore, dPPA treatment inhibited the insulin-stimulated tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and the threonine and serine phosphorylation of PKB by ∼50% in the soleus. dPPA treatment also caused serine phosphorylation of IRS-1 in the slow-twitch soleus muscle. In conclusion, our results show that phorbol esters stimulate glucose transport in fast-twitch skeletal muscles and inhibit insulin signaling in slow-twitch soleus muscle of rats. These findings suggest that mechanisms other than PKC activation mediate lipotoxicity-induced whole body insulin resistance.

Effects of Exercise on Lactate Transport Into Mouse Skeletal Muscles

1994 ◽  
Vol 19 (3) ◽  
pp. 275-285 ◽  
Author(s):  
Arend Bonen ◽  
Karl J. A. McCullagh
Keyword(s):  
Skeletal Muscle ◽  
Key Words ◽  
Muscle Glycogen ◽  
Skeletal Muscles ◽  
Treadmill Exercise ◽  
Lactate Transport ◽  
Muscle Lactate ◽  
Slow Twitch ◽  
Fast Twitch

Skeletal muscle lactate transport was investigated in vitro in isolated fast-twitch (EDL) and slow-twitch soleus (Sol) skeletal muscles from control and exercised mice. Exercise (23 m/min, 8% grade) reduced muscle glycogen by 37% in EDL (p < 0.05) and by 35% in Sol muscles (p < 0.05). Lactate transport measurements (45 sec) were performed after 60 min of exercise in intact EDL and Sol muscles in vitro, at differing pH (6.5 and 7.4) and differing lactate concentrations (4 and 30 mM). Lactate transport was observed to be greater in Sol than in EDL (p < 0.05). In the exercised muscles there was a small but significant increase in lactate transport (p < 0.05). Lactate transport was greater when exogenous lactate concentrations were greater (p < 0.05) and more rapid at the lower pH (p < 0.05). These studies demonstrated that lactate transport was increased with exercise. Key words: soleus, EDL, treadmill exercise

Lactate transport studied in sarcolemmal giant vesicles from rat skeletal muscles: effect of denervation

1995 ◽  
Vol 269 (4) ◽  
pp. E679-E682 ◽  
Author(s):  
H. Pilegaard ◽  
C. Juel
Keyword(s):  
Skeletal Muscles ◽  
Transport Capacity ◽  
Lactate Transport ◽  
Giant Vesicles ◽  
Muscle Lactate ◽  
Ldh Activity ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Sarcolemmal Vesicles ◽  
White Gastrocnemius

The effect of denervation on lactate transport capacity was studied in giant sarcolemmal vesicles obtained from rat muscle. The rate of lactate transport was determined in soleus and red (RG) and white gastrocnemius (WG) after 1, 3, and 21 days of denervation and in the corresponding contralateral muscles. In addition, muscle lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activities were determined. After 1, 3, and 21 days of denervation the rate of lactate transport was lower (P < 0.05) in WG (9, 11, and 36%), RG (15, 21, and 41%), and soleus (12, 24, and 50%) compared with the contralateral muscles. After 21 days of denervation LDH activity was 26, 25, and 34% and SDH activity 33, 25, and 27% lower (P < 0.05) in WG, RG, and soleus, respectively, compared with the contralateral muscles. In the control muscles the lactate transport capacity was 20 and 32% lower (P < 0.05) in WG than in RG and soleus, respectively. The present findings provide support that the sarcolemmal lactate carrier is a plastic system; the transport capacity in soleus, RG, and WG already declines after 1 day of denervation and is further reduced after 21 days of denervation. In addition, the data suggest that the lactate transport capacity in fast-twitch glycolytic fibers < fast-twitch oxidative-glycolytic fibers < slow-twitch oxidative fibers.

Myosin light chain phosphorylation in fast and slow skeletal muscles in situ

1984 ◽  
Vol 247 (5) ◽  
pp. C462-C471 ◽  
Author(s):  
R. L. Moore ◽  
J. T. Stull
Keyword(s):  
Skeletal Muscle ◽  
Light Chain ◽  
Skeletal Muscles ◽  
Myosin Light Chain ◽  
White Muscle ◽  
Slow Muscle ◽  
Phosphate Content ◽  
Slow Twitch ◽  
Fast Twitch

The physiological properties of contraction-induced phosphate incorporation into the phosphorylatable light chain (P-light chain) of myosin were examined in fast-twitch white, fast-twitch red, and slow-twitch skeletal muscles in situ. Neural stimulation of rat gastrocnemius muscles between 0.5 and 100 Hz produced an increase in the phosphate content of the P-light chain from the white portion of the muscle, and the rate of P-light chain phosphorylation was frequency dependent. The extent of phosphorylation of P-light chain from the fast-twitch red portion of the gastrocnemius muscle was less. In contrast to fast-twitch skeletal muscle, only high-frequency stimulation (30-100 Hz) produced a small increase in the phosphate content of P-light chain from the slow-twitch soleus muscle. Fast white muscle contained 2.2 and 3.5 times more myosin light chain kinase activity than did the fast red and slow muscle, respectively. The rate of P-light chain dephosphorylation was four times faster in slow muscle than in fast white muscle. Thus the greater extent of phosphorylation of P-light chain in fast-twitch white skeletal muscle fibers may be due in part to the presence of more kinase and less phosphatase activities. Isometric twitch tension potentiation was correlated to the extent of phosphorylation of P-light chain from fast white muscle. The physiological consequences of P-light chain phosphorylation are likely to be of greatest importance in fast-twitch white muscle.

Studies of the halothane-cooling contractures of skeletal muscle

1987 ◽  
Vol 65 (4) ◽  
pp. 697-703 ◽  
Author(s):  
Roberto T. Sudo ◽  
Gisele Zapata ◽  
Guilherme Suarez-Kurtz
Keyword(s):  
Skeletal Muscle ◽  
Synergistic Effects ◽  
Rabbit Muscle ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Dose Dependent ◽  
Muscle Biopsies ◽  
Ca Homeostasis ◽  
Potential Use

The characteristics of transient contractures elicited by rapid cooling of frog or mouse muscles perfused in vitro with solutions equilibrated with 0.5–2.0% halothane are reviewed. The data indicate that these halothane-cooling contractures are dose dependent and reproducible, and their amplitude is larger in muscles containing predominantly slow-twitch type fibers, such as the mouse soleus, than in muscles in which fast-twitch fibers predominate, such as the mouse extensor digitorum longus. The halothane-cooling contractures are potentiated in muscles exposed to succinylcholine. The effects of Ca2+-free solutions, of the local anesthetics procaine, procainamide, and lidocaine, and of the muscle relaxant dantrolene on the halothane-cooling contractures are consistent with the proposal that the halothane-cooling contractures result from synergistic effects of halothane and low temperature on Ca sequestration by the sarcoplasmic reticulum. Preliminary results from skinned rabbit muscle fibers support this proposal. The halothane concentrations required for the halothane-cooling contractures of isolated frog or mouse muscles are comparable with those observed in serum of patients during general anesthesia. Accordingly, fascicles dissected from muscle biopsies of patients under halothane anesthesia for programmed surgery develop large contractures when rapidly cooled. The amplitude of these halothane-cooling contractures declined with the time of perfusion of the muscle fascicles in vitro with halothane-free physiological solutions. It is suggested that the halothane-cooling contractures could be used as a simple experimental model for the investigation of the effects of halothane on Ca homeostasis and contractility in skeletal muscle and for study of drugs of potential use in the management of the contractures associated with the halothane-induced malignant hyperthermia syndrome. It is shown that salicylates, but not indomethacin or mefenamic acid, inhibit the halothane-cooling contractures.

scholarly journals The Functional Role of Calcineurin in Hypertrophy, Regeneration, and Disorders of Skeletal Muscle

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Kunihiro Sakuma ◽  
Akihiko Yamaguchi
Keyword(s):  
Skeletal Muscle ◽  
Functional Role ◽  
Muscular Hypertrophy ◽  
Growth And Remodeling ◽  
Muscular Disorders ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Calcineurin Activity ◽  
Muscle Remodeling

Skeletal muscle uses calcium as a second messenger to respond and adapt to environmental stimuli. Elevations in intracellular calcium levels activate calcineurin, a serine/threonine phosphatase, resulting in the expression of a set of genes involved in the maintenance, growth, and remodeling of skeletal muscle. In this review, we discuss the effects of calcineurin activity on hypertrophy, regeneration, and disorders of skeletal muscle. Calcineurin is a potent regulator of muscle remodeling, enhancing the differentiation through upregulation of myogenin or MEF2A and downregulation of the Id1 family and myostatin. Foxo may also be a downstream candidate for a calcineurin signaling molecule during muscle regeneration. The strategy of controlling the amount of calcineurin may be effective for the treatment of muscular disorders such as DMD, UCMD, and LGMD. Activation of calcineurin produces muscular hypertrophy of the slow-twitch soleus muscle but not fast-twitch muscles.

Increased lipoprotein lipase activity of skeletal muscle in cold-acclimated rats

1977 ◽  
Vol 55 (12) ◽  
pp. 1241-1243 ◽  
Author(s):  
N. Bégin-Heick ◽  
H. M. C. Heick
Keyword(s):  
Skeletal Muscle ◽  
Cold Acclimation ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Skeletal Muscles ◽  
Lipoprotein Lipase Activity ◽  
Slow Twitch ◽  
Respiratory Movements ◽  
Parallel Fashion

The activity of lipoprotein lipase (LPL) in the heart, diaphragm, and soleus muscles was markedly increased in cold-acclimated rats and it was even greater in rats treated with oxytetracycline (OTC) while exposed to cold. Other skeletal muscles studied had low and variable activities which were not significantly increased by cold acclimation or by cold plus OTC treatment. It appears therefore that, apart from the heart and the muscles involved in respiratory movements, LPL activity is primarily associated with those muscles which contain a predominance of slow-twitch oxidative fibers, and that the enzyme in muscle, heart, and diaphragm responds to cold acclimation and cold plus OTC treatment in a parallel fashion in these tissues.

Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles

1998 ◽  
Vol 84 (2) ◽  
pp. 593-598 ◽  
Author(s):  
Michael K. Connor ◽  
David A. Hood
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Activity ◽  
Skeletal Muscles ◽  
Male Rats ◽  
Mitochondrial Enzymes ◽  
Mrna Levels ◽  
Triceps Brachii ◽  
Protein Levels ◽  
Functional Consequences ◽  
Microgravity Conditions

Connor, Michael K., and David A. Hood. Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles. J. Appl. Physiol. 84(2): 593–598, 1998.—The purpose of this study was to examine the expression of nuclear and mitochondrial genes in cardiac and skeletal muscle (triceps brachii) in response to short-duration microgravity exposure. Six adult male rats were exposed to microgravity for 6 days and were compared with six ground-based control animals. We observed a significant 32% increase in heart malate dehydrogenase (MDH) enzyme activity, which was accompanied by a 62% elevation in heart MDH mRNA levels after microgravity exposure. Despite modest elevations in the mRNAs encoding subunits III, IV, and VIc as well as a 2.2-fold higher subunit IV protein content after exposure to microgravity, heart cytochrome c oxidase (CytOx) enzyme activity remained unchanged. In skeletal muscle, MDH expression was unaffected by microgravity, but CytOx activity was significantly reduced 41% by microgravity, whereas subunit III, IV, and VIc mRNA levels and subunit IV protein levels were unaltered. Thus tissue-specific (i.e., heart vs. skeletal muscle) differences exist in the regulation of nuclear-encoded mitochondrial proteins in response to microgravity. In addition, the expression of nuclear-encoded proteins such as CytOx subunit IV and expression of MDH are differentially regulated within a tissue. Our data also illustrate that the heart undergoes previously unidentified mitochondrial adaptations in response to short-term microgravity conditions more dramatic than those evident in skeletal muscle. Further studies evaluating the functional consequences of these adaptations in the heart, as well as those designed to measure protein turnover, are warranted in response to microgravity.

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