Human Skeletal Muscle Phosphorylase Activities with Exercise and Training

Taylor, Aimee R; Booth, Morgan; S, Rao

doi:10.1139/y72-150

Cited by 12 publications

(4 citation statements)

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“…All these adaptations contribute to the increased lipid metabolism and 'glycogen sparing' reported for a given submaximal workload following training. In apparent contradiction to these adaptations, Taylor et al (1972b) reported that phosphorylase activity was significantly increased by endurance training. Taylor et al (1971) also re->,orted that glycogen utilisation was greater following training for a work regimen in which the subjects worked at between 60 and 80% V02max.…”

Section: Glycogen Response To Endurance Trainingmentioning

confidence: 99%

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Acute and Chronic Responses of Skeletal Muscle to Endurance and Sprint Exercise

1990

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Skeletal muscle adapts to the stress of endurance and sprint exercise and training. There are 2 main types of skeletal muscle fibre--slow twitch (ST) and fast twitch (FTa, FTb, FTc). Exercise may produce transitions between FT and ST fibres. Sprint training has decreased the proportion of ST fibres and significantly increased the proportion of FTa fibres, while endurance training may convert FTb to FTa fibres, and increase the proportion of ST fibres (i.e. FTb----FTa----FTc----ST). However, the high proportion of ST fibres documented for elite endurance athletes may be simply the result of natural selection. ST fibres function predominantly during submaximal exercise, whereas FT fibres are recruited as exercise intensity approaches VO2max and/or glycogen stores are depleted. Long distance runners have greater ST and FT fibre areas than untrained controls. However, doubt remains as to whether the ST or FT fibre area is greatest in endurance athletes. Increases in FT fibre area seem to occur during the first 2 months of training whereas ST fibre areas appear to increase after 2 to 6 months of training. Sprint training leads to the preferential use of FT fibres and male, but not female sprinters have larger FT fibres than untrained controls. Mitochondrial proteins and oxidative enzymes, as opposed to VO2max, are important determinants of the duration of endurance exercise. Endurance training increases intramuscular glycogen stores in both FT and ST fibres and produces a 'glycogen-sparing' effect which is characterised by an increased free fatty acid (FFA) metabolism. The activity of glycogen synthase is also increased by endurance training. Sprint training increases glycogen concentrations similarly in all fibre types, reduces the rate of glycogen utilisation at submaximal workloads and allows supramaximal workloads to be maintained for longer periods of time. During endurance exercise the pattern of glycogen depletion varies between muscle fibre types and between muscle groups. Glycogen stores in ST fibres are utilised initially, followed by stores in FTa then FTb fibres. Sprint activities are associated with a much greater rate of glycogen depletion. However, it is unlikely that glycogen depletion causes fatigue during sprinting. Sprint work is associated with a preferential depletion of glycogen from FTb then FTa and ST fibres. Endurance training appears to increase triglyceride stores adjacent to mitochondria and ST fibres have greater triglyceride stores than FT fibres. Endurance exercise is associated with a preferential use of triglycerides from ST fibres and endogenous triglycerides may account for over 50% of the total lipid oxidised during exercise.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Glycogen Response To Endurance Trainingmentioning

confidence: 99%

“…Finally, phosphorylase a activity is significantly reduced by fatiguing endurance activity in trained and untrained individuals (Taylor et al 1972b). …”

Section: Acute Glycogen Response To Endurance Exercisementioning

confidence: 99%

Acute and Chronic Responses of Skeletal Muscle to Endurance and Sprint Exercise

1990

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“…There have been few quantitative studies of phosphorylase activity in human skeletal muscle (2, 5, 18,21) and in only one of these (2) was the enzyme assayed in the direction of glycogen breakdown. This latter study was made using samples of m. erector trunci.…”

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confidence: 99%

Glycogen Phosphorylase Activity in Biopsy Samples and Single Muscle Fibres of Musculus Quadriceps Femoris of Man at Rest

Harris

Essén

Hultman

1976

Scandinavian Journal of Clinical and Laboratory Investigation

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Glycogen phosphorylase activity in biopsy samples of the quadriceps muscle of man taken at rest was measured in the direction of glycogen breakdown. The conditions of assay used were pH 6.8 and 35 degrees C. Mean phosphorylase activity per kg fresh muscle in 8 male volunteers was: phosphorylase a - 259 U, and total phosphorylase - 627 U, where 1 U is the production of 1 mumol glucose-1-phosphate/s under the conditions of assay. The mean value of total activity, transposed to the in vivo condition, is sufficient to support a maximum rate of glycogen degradation calculated as glucosyl units utilized per kg fresh muscle, of 627 mumol/s. This is approximately the rate at which glycolysis occurs during a maximum voluntary isometric contraction. The mean ratio of phosphorylase a activity to total activity at rest was 0.40. Estimates of the mean total phosphorylase activity in type I ('slow') muscle fibres isolated from the quadriceps of 9 volunteers ranged from 210-385 U/kg fresh muscle, and in type II ('fast') muscle fibres from 493-934 U/kg fresh muscle. The average ratio of activity in type II fibres compared with that in type I fibres was 2.5.

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“…Only sparse information is available on enzyme activities in human skeletal muscles [6,18,37,41,42,46,48]. Moreover, the determinations are from different muscles and from biopsies taken with different techniques which may influence the level of activity.…”

Section: Discussionmentioning

confidence: 99%

Incorporation Rate of Glucose Carbon, Palmitate Carbon and Leucine Carbon into Metabolites in Relation to Enzyme Activities and RNA Levels in Human Skeletal Muscles

Bylund¹,

Holm²,

Lundholm³

et al. 1976

Enzyme

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The activities (Vmax) of hexokinase, glycogen phosphorylase, glucose-6- phosphate dehydrogenase, phosphofructokinase, lactate dehydrogenase, citrate synthase, cytochrome c oxidase, and 3-OH-acyl-CoA dehydrogenase in human skeletal muscles were compared with the in vitro utilization of glucose and palmitic acid assessed under optimal conditions. Statistically significant correlations between substrate fluxes and enzyme activities were found suggesting that the substrate incorporation rate in vitro in some way reflects the capacity of metabolic pathways. The incorporation rate of leucine into muscle proteins was also statistically significantly correlated to the RNA concentration in the muscle tissue. Glycolytic and glycogenolytic enzymes correlated significantly to each other and correlations were also found between aerobic enzymes supporting the validity of constant proportions between certain key enzymes in human skeletal muscles.

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Human Skeletal Muscle Phosphorylase Activities with Exercise and Training

Cited by 12 publications

References 0 publications

Acute and Chronic Responses of Skeletal Muscle to Endurance and Sprint Exercise

Acute and Chronic Responses of Skeletal Muscle to Endurance and Sprint Exercise

Glycogen Phosphorylase Activity in Biopsy Samples and Single Muscle Fibres of Musculus Quadriceps Femoris of Man at Rest

Incorporation Rate of Glucose Carbon, Palmitate Carbon and Leucine Carbon into Metabolites in Relation to Enzyme Activities and RNA Levels in Human Skeletal Muscles

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