In vitro studies on the effect of glucocorticoids on the metabolism of perfused rat skeletal muscle

The branched chain 2-oxo acid dehydrogenase from rat skeletal muscle, heart, kidney and liver mitochondria can undergo a reversible activation-inactivation cycle in vitro. Similar results were obtained with the enzyme from kidney mitochondria of pig and cow. The dehydrogenase is markedly inhibited by ATP and the inhibition is not reversed by removing the nucleotide. The non-metabolizable ATP analogue adenosine 5′-[beta gamma-imido] triphosphate can block the effect of ATP when added with the nucleotide, but has no effect by itself, nor can it reverse the inhibition in mitochondria preincubated with ATP. These findings suggest that the branched chain 2-oxo acid dehydrogenase undergoes a stable modification that requires the splitting of the ATP gamma-phosphate group. In skeletal muscle mitochondria the rate of inhibition by ATP is decreased by oxo acid substrates and enhanced by NADH. The dehydrogenase can be reactivated 10-20 fold by incubation at pH 7.8 in a buffer containing Mg2+ and cofactors. Reactivation is blocked by NaF (25 mM). The initial activity of dehydrogenase extracted from various tissues of fed rats varies considerably. Activity is near maximal in kidney and liver whereas the dehydrogenase in heart and skeletal muscle is almost completely inactivated. These studies emphasize that comparisons of branched chain 2-oxo acid dehydrogenase activity under various physiological conditions or in different tissues must take into account its state of activation. Thus the possibility exists that the branched chain 2-oxo acid dehydrogenase may be physiologically regulated via a covalent mechanism.

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Properties of 5′-deiodinase of 3,3′,5′-triiodothyronine in rat skeletal muscle

Acta Endocrinologica ◽

10.1530/acta.0.1200069 ◽

1989 ◽

Vol 120 (1) ◽

pp. 69-74 ◽

Cited By ~ 4

Author(s):

Fujiko Tsukahara ◽

Teruko Nomoto ◽

Michiko Maeda

Keyword(s):

Skeletal Muscle ◽

Drinking Water ◽

Incubation Medium ◽

Marked Reduction ◽

Daily Administration ◽

Type I ◽

Rat Skeletal Muscle ◽

Thyroid Status ◽

Altered Thyroid

Abstract. To characterize rT3 5′-deiodinase (5′D) in rat skeletal muscle, the effects of altered thyroid status and PTU on rT3 5′D were studied. rT3 5′D activity was measured by incubating homogenates of rat skeletal muscle with [125]rT3, iodine labelled in the outer ring, in the presence of 20 mmol/l DL-dithiothreitol. This activity was observed to increase significantly 24 h after a single sc injection of T3 (75 μg/kg). The increase following the daily administration of this drug (15 or 75 μg/kg) for 3 and 14 days was dependent on the dose and number of previous days of injection. A significant decrease in activity was observed 2 weeks after thyroidectomy. The addition of 0.1 mmol/l 6-n-propyl-2-thiouracil (PTU) to the incubation medium in vitro caused a marked reduction in the activity in homogenates of skeletal muscle from hypothyroid, euthyroid and hyperthyroid rats. PTU, present at 0.05% in the drinking water for 2 weeks virtually abolished it. The properties of rT3 5′D in rat skeletal muscle thus appear to be essentially the same as those of type I enzyme with respect to response toward altered thyroid status and PTU.

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Characterization of β-adrenoceptors on rat skeletal muscle cells grown in vitro

Biochemical Pharmacology ◽

10.1016/0006-2952(90)90491-3 ◽

1990 ◽

Vol 40 (5) ◽

pp. 1043-1048 ◽

Cited By ~ 11

Author(s):

Marie-Helene Disatnik ◽

Sanford R. Sampson ◽

Asher Shainberg

Keyword(s):

Skeletal Muscle ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Rat Skeletal Muscle

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AMP-activated protein kinase activity and glucose uptake in rat skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2001.280.5.e677 ◽

2001 ◽

Vol 280 (5) ◽

pp. E677-E684 ◽

Cited By ~ 152

Author(s):

Nicolas Musi ◽

Tatsuya Hayashi ◽

Nobuharu Fujii ◽

Michael F. Hirshman ◽

Lee A. Witters ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Kinase ◽

Glucose Uptake ◽

Muscle Contractions ◽

Treadmill Running ◽

Dependent Manner ◽

Rat Skeletal Muscle ◽

Amp Activated Protein Kinase ◽

Dose Dependent

The AMP-activated protein kinase (AMPK) has been hypothesized to mediate contraction and 5-aminoimidazole-4-carboxamide 1-β-d-ribonucleoside (AICAR)-induced increases in glucose uptake in skeletal muscle. The purpose of the current study was to determine whether treadmill exercise and isolated muscle contractions in rat skeletal muscle increase the activity of the AMPKα1 and AMPKα2 catalytic subunits in a dose-dependent manner and to evaluate the effects of the putative AMPK inhibitors adenine 9-β-d-arabinofuranoside (ara-A), 8-bromo-AMP, and iodotubercidin on AMPK activity and 3- O-methyl-d-glucose (3-MG) uptake. There were dose-dependent increases in AMPKα2 activity and 3-MG uptake in rat epitrochlearis muscles with treadmill running exercise but no effect of exercise on AMPKα1 activity. Tetanic contractions of isolated epitrochlearis muscles in vitro significantly increased the activity of both AMPK isoforms in a dose-dependent manner and at a similar rate compared with increases in 3-MG uptake. In isolated muscles, the putative AMPK inhibitors ara-A, 8-bromo-AMP, and iodotubercidin fully inhibited AICAR-stimulated AMPKα2 activity and 3-MG uptake but had little effect on AMPKα1 activity. In contrast, these compounds had absent or minimal effects on contraction-stimulated AMPKα1 and -α2 activity and 3-MG uptake. Although the AMPKα1 and -α2 isoforms are activated during tetanic muscle contractions in vitro, in fast-glycolytic fibers, the activation of AMPKα2-containing complexes may be more important in regulating exercise-mediated skeletal muscle metabolism in vivo. Development of new compounds will be required to study contraction regulation of AMPK by pharmacological inhibition.

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Insulin and Contraction Directly Stimulate UCP2 and UCP3 mRNA Expression in Rat Skeletal Muscle in Vitro

Biochemical and Biophysical Research Communications ◽

10.1006/bbrc.2001.4736 ◽

2001 ◽

Vol 283 (1) ◽

pp. 19-25 ◽

Cited By ~ 50

Author(s):

Steen B. Pedersen ◽

Sten Lund ◽

Esben S. Buhl ◽

Bjørn Richelsen

Keyword(s):

Skeletal Muscle ◽

Mrna Expression ◽

Rat Skeletal Muscle

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Excitation-Contraction Coupling in Rat Skeletal Muscle Cells: Evolution During in Vitro Myogenesis

Excitation-Contraction Coupling in Skeletal, Cardiac, and Smooth Muscle - Advances in Experimental Medicine and Biology ◽

10.1007/978-1-4615-3362-7_6 ◽

1992 ◽

pp. 73-89 ◽

Cited By ~ 2

Author(s):

Christian Cognard ◽

Bruno Constantin ◽

Michèle Rivet ◽

Nathalie Imbert ◽

Colette Besse ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Rat Skeletal Muscle ◽

Excitation Contraction Coupling ◽

Contraction Coupling

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N tau-methylhistidine release: contributions of rat skeletal muscle, GI tract, and skin

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1982.243.4.e293 ◽

1982 ◽

Vol 243 (4) ◽

pp. E293-E297 ◽

Cited By ~ 2

Author(s):

S. J. Wassner ◽

J. B. Li

Keyword(s):

Skeletal Muscle ◽

Gastrointestinal Tract ◽

Soft Tissue ◽

Fractional Catabolic Rate ◽

Gi Tract ◽

Rat Skeletal Muscle ◽

Catabolic Rate ◽

Total Body

The relative contributions of skeletal muscle, gastrointestinal tract, and skin to urinary N tau-methylhistidine (MH) excretion were estimated during in vitro studies using the rat hemicorpus preparation. After 0.5 h of perfusion, MH release into the perfusate was linear for 3 h and averaged 29.8 nmol . h-1 . 100 g hemicorpus-1. In vivo, 24-h urinary MH excretion averaged 37.3 nmol . h-1 . 100 g body wt-1. The ratio of soft tissue to skin weight is equal (3.2:1) in the whole rat and in the hemicorpus. The gastrointestinal tract released 16.0 nmol . h-1 . 100 g body wt-1 or approximately 41% of the total urinary MH excretion. Preparations perfused with or without skin showed modest differences in the rate of MH release that were not statistically significant. Skeletal muscle contains 89.8% of total body MH content, whereas gastrointestinal tract and skin contain 3.8 and 6.4%, respectively. Gastrointestinal tract actomyosin turns over rapidly with a fractional catabolic rate of 24%/day versus 1.4%/day for skeletal muscle actomyosin.

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Regulation of CPT I activity in intermyofibrillar and subsarcolemmal mitochondria from human and rat skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00237.2003 ◽

2004 ◽

Vol 286 (1) ◽

pp. E85-E91 ◽

Cited By ~ 32

Author(s):

Veronic Bezaire ◽

George J. F. Heigenhauser ◽

Lawrence L. Spriet

Keyword(s):

Skeletal Muscle ◽

Vastus Lateralis ◽

Moderate Intensity ◽

Rat Skeletal Muscle ◽

Moderate Intensity Exercise ◽

Mitochondrial Fractions ◽

Decreasing Ph ◽

Subsarcolemmal Mitochondria ◽

Cpt I

Carnitine palmitoyltransferase I (CPT I) is considered the rate-limiting enzyme in the transfer of long-chain fatty acids (LCFA) into the mitochondria and is reversibly inhibited by malonyl-CoA (M-CoA) in vitro. In rat skeletal muscle, M-CoA levels decrease during exercise, releasing the inhibition of CPT I and increasing LCFA oxidation. However, in human skeletal muscle, M-CoA levels do not change during moderate-intensity exercise despite large increases in fat oxidation, suggesting that M-CoA is not the sole regulator of increased CPT I activity during exercise. In the present study, we measured CPT I activity in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondria isolated from human vastus lateralis (VL), rat soleus (Sol), and red gastrocnemius (RG) muscles. We tested whether exercise-related levels (∼65% maximal O2 uptake) of calcium and adenylate charge metabolites (free AMP, ADP, and Pi) could override the M-CoA-induced inhibition of CPT I activity and explain the increased CPT I flux during exercise. Protein content was ∼25-40% higher in IMF than in SS mitochondria in all muscles. Maximal CPT I activity was similar in IMF and SS mitochondria in all muscles (VL: 282 ± 46 vs. 280 ± 51; Sol: 390 ± 81 vs. 368 ± 82; RG: 252 ± 71 vs. 278 ± 44 nmol·min-1·mg protein-1). Sensitivity to M-CoA did not differ between IMF and SS mitochondria in all muscles (25-31% inhibition in VL, 52-70% in Sol and RG). Calcium and adenylate charge metabolites did not override the M-CoA-induced inhibition of CPT I activity in mitochondria isolated from VL, Sol, and RG muscles. Decreasing pH from 7.1 to 6.8 reduced CPT I activity by ∼34-40% in both VL mitochondrial fractions. In summary, this study reports no differences in CPT I activity or sensitivity to M-CoA between IMF and SS mitochondria isolated from human and rat skeletal muscles. Exercise-induced increases in calcium and adenylate charge metabolites do not appear responsible for upregulating CPT I activity in human or rat skeletal muscle during moderate aerobic exercise.

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