Changes In Skeletal Muscle Metabolism Research Articles

Spinal cholinergic inhibition of the pressor response to skeletal muscle activation

The purpose of this study was to delineate the role of the cholinergic pathway within the spinal cord in the reflex cardiovascular responses to muscle activity. Based on dose–response experiments, we microdialyzed a 0.1 mM solution of the acetylcholinesterase inhibitor neostigmine into the L7 level of the dorsal horn of anesthetized cats to determine its effects on the mean arterial blood pressure (MAP) and heart rate (HR) responses to static muscle contraction or passive stretch. The peak responses to 1-min contractions and stretches were reduced from control levels after 1 h of drug administration. In four experiments, the cardiovascular responses returned to control levels after a 2-h recovery period. Perfusion of the cholinergic receptor antagonist atropine accentuated the peak MAP response to muscle contraction. By contrast, atropine administration had no effect on the peak MAP adjustment to passive muscle stretch. These data support the hypothesis that increased acetylcholine (ACh) concentrations in the spinal cord inhibit the reflex cardiovascular responses to static muscle contraction. Further, the results suggest that the spinal cholinergic system is activated by metabolic changes in skeletal muscle, but likely unaffected by mechanical muscle changes.

QUANTITATIVE DYNAMIC IMAGING OF PERFUSION IN HUMAN SKELETAL MUSCLE DURING EXERCISE WITH ARTERIAL SPIN LABELIN

1351 Measuring the dynamics of blood flow and metabolic changes in skeletal muscle during exercise is important for understanding aspects of muscle physiology. The acquisition of both spatially and temporally localized perfusion measurements within working muscle is desirable, but is difficult to obtain. Standard methods that can achieve temporal resolution, such as blood-gas extraction, thermodilution, or plethysmography, allow measurements from entire muscle groups but cannot resolve activity within muscle groups. Methods using microspheres, on the other hand, are able to determine the spatial distribution of flow at one time point but are more difficult to use for the study of dynamics because of the need to use distinguishable microspheres for each time point. We have used magnetic resonance images acquired using an arterial spin labeling technique to show spatial and temporal variations of perfusion in the skeletal muscle of exercising humans. This technique involves magnetically tagging blood proximal to an imaging slice, then observing the changes that occur as the blood flows into that slice. Measurements are made directly from rapidly acquired MR images, and so provide both spatial and temporal information. Because no contrast agent is used, they are completely non-invasive. Measured perfusion values were consistent with those obtained with traditional techniques reported in the literature. This method can provide a useful tool in the study of muscle physiology.

Technetium-99m sestamibi leg scintigraphy for non-invasive assessment of propionyl- l -carnitine induced changes in skeletal muscle metabolism

Technetium-99m sestamibi leg scintigraphy for non-invasive assessment of propionyl- l -carnitine induced changes in skeletal muscle metabolism

Structural and metabolic changes in skeletal muscle of cold acclimated rats

1. 1. The effects of long-term (8 weeks), intermittent (16 h daily), cold exposure (4–5 ± 1°C) on pectoralis, diaphragm and gastrocnemius muscles of rat were studied. 2. 2. Cold acclimation resulted in marked morphological aberrations in the constituent muscle fibers coupled with metabolic changes recognized as early on as the first week. 3. 3. The activities of all enzymes and total lipids witnessed an increase notably in red and intermediate muscle fibers during prolonged acclimation. 4. 4. A measurement of the cross sectional dimensions and populations of the different fiber types suggested an overall tendency among the three muscles to undergo a fiber transformation during cold acclimation.

Skeletal muscle fiber composition and capillarization in patients with chronic heart failure: Relation to exercise capacity and central hemodynamics

Patients with chronic heart failure have structural and metabolic changes in skeletal muscle, which may be of importance for symptomatology. The origin of these changes are still unknown. The relationship between fiber composition and capillarization in skeletal muscle with exercise capacity and central hemodynamic variables was examined. Biopsies from the lateral vastus muscle were taken in 12 patients with chronic heart failure. Samples from eight normal subjects served as control samples. All patients underwent maximal exercise tests. Central hemodynamic variables were measured during exercise in five patients. The patients had a higher percentage of type II B fibers ( P = .03) and fewer capillaries per fiber ( P = .02) than the controls subjects. VO 2 max correlated with the percentage of type I fibers, whereas the correlation with the type II A fibers was inverse. Cardiac index and pulmonary capillary wedge pressure at submaximal and maximal exercise were related to fiber type composition and relative fiber areas. Skeletal muscle fiber type composition and capillarization was changed in patients with chronic heart failure. These changes might influence exercise capacity. There were relationships between central hemodynamic variables and skeletal muscle changes. What the cause and effects were need further investigation.

Physical training improves skeletal muscle metabolism in patients with chronic heart failure

Objectives. This study investigated the effects of physical training on skeletal muscle metabolism in patients with chronic heart failure.Background. Skeletal muscle metabolic abnormalities in patients with chronic heart failure have been associated with exercise intolerance. Muscle deconditioning is a possible mechanism for the intrinsic skeletal muscle metabolic changes seen in chronic heart failure.Methods. We used phosphorus-31 nuclear magnetic resonance spectroscopy to study muscle metabolism during exercise in 12 patients with stable ischemic chronic heart failure undergoing 8 weeks of home-based bicycle exercise training in a randomized crossover controlled trial. Changes in muscle pH and concentrations of phosphocreatine and adenosine diphosphate (ADP) were measured in phosphorus-31 spectra of calf muscle obtained at rest, throughout incremental work load plantar flexion until exhaustion and during recovery from exercise. Results were compared with those in 15 age-matched control subjects who performed a single study only.Results. Before training, phosphocreatine depletion, muscle acidification and the increase in ADP during the 1st 4 min of plantar flexion exercise were all increased (p < 0.04) compared with values in control subjects. Training produced an increase (p < 0.002) in incremental plantar flexion exercise tolerance. After training, phosphocreatine depletion and the increase in ADP during exercise were reduced significantly (p < 0.003) at all matched submaximal work loads and at peak exercise, although there was no significant change in the response of muscle pH to exercise. After training, changes in ADP were not significantly different from those in control subjects, although phosphocreatine depletion was still greater (p < 0.05) in trained patients than in control subjects. The phosphocreatine recovery half-time was significantly (p < 0.05) shorter after training, althrough there was no significant change in the half-time of adenosine diphosphate recovery. In untrained subjects, the initial rate of phosphocreatine resynthesis after exercise (a measure of the rate of oxidative adenosine triphosphate [ATP]synthesis) and the inferred maximal rate of mitochondrial ATP synthesis were reduced compared with rates in control subjects (p < 0.003) and both were significantly increased (p < 0.05) by training, so that they were not significantly different from values in control subjects.Conclusions. The reduction in phosphocreatine depletion and in the increase in ADP during exercise, and the enhanced rate of phosphocreatine resynthesis in recovery (which is independent of muscle mass) indicate that a substantial correction of the impaired oxidative capacity of skeletal muscle in chronic heart failure can be achieved by exercise training.

Simultaneous electromyography and 31P nuclear magnetic resonance spectroscopy — with application to muscle fatigue

The electromyogram (EMG) is often used to study human muscle fatigue, but the changes in the electromyographic signals during muscle contraction are not well understood in relation to muscle metabolism. The 31P NMR spectroscopy is a semi-quantitative non-invasive method for studying the metabolic changes in human muscle. The aim of this study was to develop a method by which EMG and NMR spectroscopy measurements could be performed simultaneously. All measurements were performed in a whole body 1.5 Tesla NMR scanner. A calf muscle ergometer, designed for use in a whole body NMR scanner, was used. The subject had the left foot strapped to the ergometer. The anterior tibial EMG was recorded by bipolar surface electrodes. A surface coil was strapped to the anterior tibial muscle next to the EMG electrodes. Simultaneous measurements of surface EMG and surface coil 31P NMR spectroscopy were performed in the scanner during an isometric submaximal voluntary contraction until exhaustion, in 6 normal volunteers. Concentrations of phosphocreatine (PCr), inorganic phosphate (P i) and pH were analysed together with root mean square (RMS) and median frequency of the EMG. The fatiguing contractions (endured 5–13 min) produced a rapid decline in PCr and pH accompanied by a rapid rise in P i. The RMS was approximately constant until the normalized PCr concentration declined below 0.6–0.7 and the pH declined below 6.75–6.85; exceeding these metabolic limits was associated with a rapidly increasing RMS value (2–3 times the previous level by exhaustion). The median frequency declined linearly with time and was found to be highly linearly correlated with the pH value ( r = 8.82). Technically, the experiments showed that it was possible to measure surface EMG and surface coil NMR spectroscopy simultaneously during isometric muscle contractions, without any known interactions. The experimental plan seems useful in understanding how metabolic changes in skeletal muscle are related to the surface electromyogram.

Metabolic changes in skeletal muscle of frog during exercise and recovery

Metabolic changes in skeletal muscle of frog during exercise and recovery

Metabolic changes in skeletal muscle and blood of greyhounds during 800-m track sprint.

The aim of this study was to examine some metabolic properties and changes that occur in skeletal muscle and blood of greyhounds after an 800-m sprint. Three prime moving fast-twitch muscles were selected: biceps femoris (BF), gastrocnemius (G), and vastus lateralis (VL). The amount of glycogen utilized during the event was 42.57, 43.86, and 42.73 mumol glucosyl units/g wet wt, respectively. Expressed as a function of race time (48.3 +/- 0.7 s, n = 3), the mean rate of glycogen breakdown was 53.48 +/- 0.5 mumol.g wet wt-1.min-1 during the sprint. This is equivalent to an ATP turnover of 160 mumol.g wet wt-1.min-1, assuming 100% anaerobic conversion to lactate. This represents a conservative estimate, since greyhound muscle is heterogeneous and comprised of a large percentage of fast-twitch oxidative fibers (Armstrong et al., Am. J. Anat. 163: 87-98, 1982). The large decrease in muscle glycogen was accompanied by a 6- to 7-fold increase in muscle lactate from 3.48 +/- 0.13 to 25.42 +/- 3.54 (BF), 2.54 +/- 1.05 to 18.96 +/- 2.60 (G), and 4.57 +/- 0.44 to 30.09 +/- 1.94 mumol.g wet wt (VL), and a fall in muscle pH from 6.88 +/- 0.03 to 6.40 +/- 0.02 (BF), 6.92 +/- 0.02 to 6.56 +/- 0.02 (G), and 6.93 +/- 0.02 to 6.47 +/- 0.01 (VL). Cytosolic phosphorylation potential in BF decreased 10-fold from 11,360 +/- 680 to 1,184 +/- 347, and redox potential decreased 5-fold, indicating a marked reduction in the cytosol at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Net substrates balance across hindlimb in conscious rabbit during late pregnancy.

The present work performed in rabbits was designed to investigate whether changes in skeletal muscle metabolism could contribute to glucose homeostasis during late pregnancy a time at which there is a large glucose demand of the gravid uterus. We therefore studied the net substrate balance of glucose, lactate, free fatty acids, and ketone bodies across the hindlimb of pregnant animals (days 24 and 30) and virgin animals. Our data show that on day 24 the basal rate of glucose uptake is similar to that observed in virgin rabbits, but it decreases by approximately 60% on day 30 despite comparable levels of blood glucose and plasma insulin at both gestational ages. A moderate hyperglycemia (20% above basal level) and hyperinsulinemia (2- to 3-fold above basal level) sustained for 80 min failed to increase glucose uptake except in virgin animals. Estimates of the contribution of substrates to oxidative metabolism indicate that free fatty acids could represent the major fuel in all groups, whereas glucose would be of minor importance especially at term. It is concluded that in pregnancy a) under normoglycemia there is a reduced insulin effect on glucose uptake and b) under moderate hyperglycemia and hyperinsulinemia the insulin resistance results from an impaired stimulation of glucose uptake. Sparing glucose from the skeletal muscle, the mother can direct more glucose toward the uterus without marked increase in her production rate.

Effect of respiratory alkalosis on skeletal muscle metabolism in the dog.

These experiments were conducted to determine whether changes in skeletal muscle metabolism contribute to the previously reported increase in whole-body O2 uptake (VO2) during respiratory alkalosis. The hind-limb and gastrocnemius-plantaris preparations in anesthetized and paralyzed dogs were used. VO2 of the hindlimb and gastrocnemius muscle was calculated from measurements of venous blood flow and arterial and venous O2 concentrations (Van Slyke analysis). Whole-body VO2 was measured by the open-circuit method. Minute ventilation (hence blood gases and pH) was controlled by a mechanical respirator. Whole-body, hind-limb, and gastrocnemius muscle VO2 increased 14, 19, and 20%, respectively, during alkalosis (P less than 0.05). In all experiments, arterial lactate concentration increased significantly (P less than 0.05) during alkalosis. A positive venoarterial lactate difference across muscle during alkalosis indicated that skeletal muscle is a source of the elevated blood lactate. We concluded that VO2 of resting skeletal muscle is increased during states of respiratory alkalosis and that this increase can account for much of the increase in whole-body VO2.

Microcirculation and hemorrhagic shock

Blood loss is followed by compensatory cardiovascular readjustments that favor the maintenance of blood flow to central vital organs rather than to peripheral tissues. The microcirculatory changes that occur in skeletal muscle in shock states are of major importance, since skeletal muscle is not only the largest cell mass of the body but also one of the major target organs for neurohumorally mediated compensatory vascular readjustments. Intravital microscopic studies show that the microvascular blood flow in skeletal muscle is intermittent in the early posthemorrhagic period. This probably reflects an interplay between α-adrenergic vasoconstrictor and β-adrenergic vasodilator activities, which serves to enhance a compensatory mobilization of interstitial fluid into the vascular compartment. A period of complete microcirculatory arrest is then seen, followed by reperfusion engaging only 30% to 50% of the capillaries that were seen perfused in resting skeletal muscle. The microvascular blood flow in shock is further characterized by a pronounced heterogeneity in distribution. Many capillaries remain constantly unperfused, while in others a slow, intermittent blood flow is seen. Obstruction of many capillaries by white blood cells and their slow passage through other capillaries seem to be the main reasons for the maldistribution of capillary blood flow in shock. Red blood cell aggregates obstructing capillary blood flow are not seen. The heterogeneous tissue perfusion is accompanied by local variations in cellular hypoxic injury, as is evidenced by multifocal measurements of tissue oxygen tension and by cellular transmembrane potential registrations. The blood-tissue exchange of substances is impaired because of the reduction in capillary surface area and changes within the interstitial compartment. Therefore, shock-induced metabolic changes in skeletal muscle remain mainly local and are not at all, or only to a limited extent, reflected in central blood. Following volume treatment the heterogeneity in capillary perfusion persists, since white blood cells often remain trapped in capillaries and obstruct blood flow. Treatment of shock with hypertonic solutions, ATP-MgCl 2, or steroids could be beneficial by enhancing the mobilization of trapped white blood cells. Microcirculatory disturbances and their local metabolic consequences in skeletal muscle of critically ill patients can be monitored in the intensive care unit by the use of microelectrodes for continuous or intermittent measurements of tissue gas tensions (P 0 2 , P CO 2 ), tissue pH, and tissue potassium levels.

Effects of penicillin G on local metabolic changes in skeletal muscle following high velocity missile injury.

The effect of systemic penicillin G treatment on the local tissue damage 12 h after a high velocity missile injury in skeletal muscle has been studied in pigs (n = 13). Blood pressure, rectal temperature, hemoglobin concentrations, hematocrits, blood gases and acid base balances were followed and the tissue levels of ATP, creatine phosphate, glucose-6-phosphate, glucose and lactate were determined in control skeletal muscle as well as in muscle samples taken from the wound area. After 12 h all devitalized tissue was debrided and weighed. Penicillin G treatment slightly diminished the local tissue metabolic deterioration and significantly reduced the amount of debrided tissue as compared to untreated animals. It may be concluded that early treatment with penicillin G will considerably diminish the local tissue damage during the first 12-hour period following a high velocity missile injury.

Relative effects of pregnancy and corticosterone administration on skeletal muscle metabolism in the rat.

The effects of pregnancy and corticosterone treatment on skeletal muscle metabolism were compared using a noncyclically perfused rat hindlimb preparation. Animal groups studied included 3-week-pregnant animals, rats injected with corticosterone (7.5 mg/100 g BW . day) for 3 days, and age-matched control rats. All were fasted 24 h before perfusion. In baseline perfusions devoid of insulin, no differences were observed among the groups with respect to muscle glucose uptake and the release of lactate, pyruvate, and glycerol. Baseline alanine and phenylalanine release were significantly increased in corticosterone-treated rats compared to values observed in control and pregnant animals. In perfusions with 100 or 500 microU/ml insulin, glucose uptake was increased 5-fold above baseline uptake in the control group. At 100 microU/ml insulin concentrations, glucose uptake in pregnant and corticosterone-treated rats achieved only 50% of the increase seen in control experiments. With 500 microU/ml insulin, glucose uptake was decreased 20% in pregnant animals and 40% in rats receiving corticosterone relative to control values. Alanine release was significantly reduced below baseline after the administration of 500 microU/ml insulin in control rats. In these rats, phenylalanine release, an index of net protein degradation, also was reduced with both 100 and 500 microU/ml insulin. Similar insulin concentrations did not suppress the efflux of either amino acid below baseline in pregnant or corticosterone-treated groups. Corticosterone administration to nonpregnant rats appears to duplicate changes in skeletal muscle metabolism that occur during late rat pregnancy. Insulin resistance in both states is manifested by a decrease in insulin-stimulated glucose uptake and an inability of insulin to suppress net muscle proteolysis. Since plasma free glucocorticoid concentrations are increased in late human as well as rat gestation, these steroids may have an important role in the development of insulin resistance at skeletal muscle sites in this state.

Local metabolic changes in skeletal muscle following high-energy missile injury.

The extent of cellular deterioration around a high-velocity missile injury was studied in canine skeletal muscle biopsies. The tissue levels of high-energy phosphates and glycolytic metabolites were analyzed in four zones surrounding the bullet tract and in an uninjured extremity. Incorporation of leucine into skeletal muscle proteins in vitro in the different zones was determined. In the tissue adjacent to the bullet tract ATP and phosphocreatine (CP) decreased significantly and remained low. No significant changes of ATP and/or CP occurred in the other zones or in the control muscle. Lactate and glucose levels increased in all zones but G6-P levels decreased in the three zones close to the wound indicating anaerobiosis and disturbed utilization of glucose. Incorporation of leucine decreased in the innermost zone and no restoration took place, but more peripherally a certain reversible decrease was seen. The present results indicate that irreversible cell damage will occur in the tissue adjacent to a high-velocity bullet tract. Reversible cellular dysfunction may occur in tissues without gross changes.

Metabolic changes in skeletal muscle during chronic metabolic acidosis

1. 1. In an attempt to clarify the importance of skeletal muscle as a source of glutamine during chronic metabolic acidosis, in vivo and in vitro experiments were performed in normal and NH 4Cl acidotic rats. 2. 2. In the acidotic animals, arterial glutamine, glutamate and alanine were significantly lower than in normal rats. The arterio-venous difference for glutamine across the hindlimb was not statistically different in acidotic and normal animals. 3. 3. No net release or uptake of glutamate was observed in either control or acidotic rats. However the uptake of alanine observed in normal animals was completely abolished in the acidotic rats. 4. 4. The metabolite profile of freeze-clamped hindlimb skeletal muscle from acidotic animals revealed a lower concentration of glutamine, glutamate, alanine, aspartate, alphaketoglutarate, lactate and pyruvate and increased ammonia concentration. 5. 5. Alanine aminotransferase activity of the hindlimb skeletal muscle was unchanged by acidosis. 6. 6. In vitro glutamine production by the isolated rat diaphragm was not different in acidotic and control animals. 7. 7. The addition of various substrates (valine, leucine and NH 4Cl) stimulated glutamine production to similar extent in control and acidotic animals. 8. 8. While alanine was produced by the diaphragm of the normal animals, it did not occur in the acidotic rats. Furthermore the addition of substrates did not stimulate alanine production by the diaphragm of the acidotic animals. 9. 9. Addition of methionine sulfoximine (MSO) 5 mM to inhibit diaphragm glutamine synthetase activity resulted in a 55% decrease in glutamine synthesis in both normal and acidotic animals. 10. 10. The production of glutamine or alanine was not affected by acidification of the incubation medium from pH 7.4 to 7.0. 11. 11. Our findings suggest that the capacity for glutamine synthesis by the skeletal muscle is not affected by metabolic acidosis. 12. 12. The fall in glutamate and the rise in ammonia concentrations in the skeletal muscle in vivo during metabolic acidosis suggest that glutamate availability is rate-limiting for the production of glutamine. This could explain the marked variations in alanine metabolism. 13. 13. In view of the very small changes observed in glutamine production by the skeletal muscle during acidosis, the role of other tissues such as the liver, the brain and, in the rat, the kidney, should be envisaged. 14. 14. The possibility of a significant decrease in glutamine metabolism by the intestine during acidosis making more glutamine available for renal extraction should also be seriously considered.

Adaptation to cold in three hours.

ARTICLESAdaptation to cold in three hoursJ LeblancJ LeblancPublished Online:01 Feb 1967https://doi.org/10.1152/ajplegacy.1967.212.2.530MoreSectionsPDF (572 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Download PDF FiguresReferencesRelatedInformation Cited ByContributions from the Land of the Maple Leaf: Canada23 September 2022Structural and metabolic changes in skeletal muscle of cold acclimated ratsJournal of Thermal Biology, Vol. 22, No. 2Habituation and dishabituation to repeated mild cold exposures in C57BL/6J micePhysiology & Behavior, Vol. 44, No. 6Thermoregulatory responses of the immature rat following repeated postnatal exposures to 2,450-MHz microwavesBioelectromagnetics, Vol. 8, No. 3Seasonal differences in thermogenic adaptation evoked by daily injections of noradrenalineJournal of Thermal Biology, Vol. 10, No. 2Effect of sodium succinate on metabolic and morphologic changes in acute cold stressBulletin of Experimental Biology and Medicine, Vol. 98, No. 4PhysiologyPhysiological characteristics of cold acclimatization in manInternational Journal of Biometeorology, Vol. 25, No. 3The correlation between colonic cooling and survival time in the acute cold-exposed laboratory mouse: Influence of cold acclimationJournal of Thermal Biology, Vol. 5, No. 3Role of Various Sites in Thermoregulatory ThermogenesisADAPTATION OF MAN TO COLDDelayed RNA changes in various neuron-neuroglia units of rat hypothalamus after short-term intermittent deep cooling with special reference to a concept of vegetative memoryActa Histochemica, Vol. 61, No. 1Nervous mechanisms and trace reactions in adaptation to coldEvidence of diurnal fluctuation of sensitivity to noradrenaline in the rat — the role of the thyroidExperientia, Vol. 32, No. 12THE ROLE OF CATECHOLAMINES IN ADAPTATION TO CHRONIC AND ACUTE STRESSThe effect of short daily cold exposures on development of brown adipose tissue in miceJournal of Comparative Physiology ? B, Vol. 98, No. 2Calorigenic effect of dopamine in ratsBulletin of Experimental Biology and Medicine, Vol. 77, No. 3Endocrine Functions during Adaptation to StressAustralian physiological research in the Antarctic and Subantarctic, with special reference to thermal stress and acclimatizationRODENTSBehavioural thermoregulation and cold adaptation in two strains of white miceInternational Journal of Biometeorology, Vol. 14, No. 3Comparative aspects of cold acclimation and nonshivering thermogenesis in homeothermsInternational Journal of Biometeorology, Vol. 13, No. 3-4 More from this issue > Volume 212Issue 2February 1967Pages 530-532 Copyright & PermissionsCopyright © 1967 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1967.212.2.530PubMed6018042History Published online 1 February 1967 Published in print 1 February 1967 Metrics