1982

DOI: 10.1007/bf01955351

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Purine nucleotide cycle as a possible anaplerotic process in rat skeletal muscle

P. W. D. Ścisłowski

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,

Z. Aleksandrowicz

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,

Julian Świerczyński

³

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Cited by 20 publications

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“…What might have caused the reduced capacity for repetitive submaximal contractions of MAD-deficient muscle, if we assume that the impaired muscle function in our subjects was indeed due to the deficiency ? MAD is an enzyme of the purine nucleotide cycle, and an important role of this cycle could be the provision of tricarboxylic acid cycle intermediates, which would be important for optimal aerobic energy production [1,18,29,30]. Therefore it could be hypothesized that failure to provide sufficient tricarboxylic acid cycle intermediates in MAD-deficient muscle, particularly during the first 5-10 min of exercise when levels of these intermediates have been found to increase substantially in healthy muscle [31][32][33], would lead to a shift of energy production towards anaerobic sources and early fatigue.…”

Section: Discussionmentioning

confidence: 99%

Muscle function during repetitive moderate-intensity muscle contractions in myoadenylate deaminase-deficient Dutch subjects

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et al. 2002

Clinical Science

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We investigated whether the capacity for repetitive submaximal muscle contraction was reduced in a group of subjects (n=8) with a primary deficiency of myoadenylate deaminase (MAD). Quadriceps femoris muscle fatigue was evaluated using voluntary and electrically stimulated contractions during 20 min of repetitive voluntary isometric contractions at 40% of maximal force-generating capacity (MFGC). After 5 min of exercise, MFGC had declined significantly to 70.6+/-4.1% (mean+/-S.E.M.) and 87.2+/-1.6% of baseline values in MAD-deficient and sedentary control subjects (n=8) respectively (P=0.002 between groups). After 5 min of exercise, the half-relaxation time had increased significantly to 113.4+/-6.1% of baseline in MAD-deficient muscle, but had decreased significantly to 94.1+/-1.3% in control subjects (P=0.003 between groups). All control subjects completed the 20-min exercise test. Five of the MAD-deficient subjects had to stop exercising due to early muscle fatigue; however, three of the MAD-deficient subjects were able to complete the 20-min exercise test. In conclusion, although the capacity for repetitive submaximal isometric muscle contractions for the group of MAD-deficient subjects was significantly decreased, it remains uncertain whether MAD deficiency is the sole cause of pronounced muscle fatigue.

“…What might have caused the reduced capacity for repetitive submaximal contractions of MAD-deficient muscle, if we assume that the impaired muscle function in our subjects was indeed due to the deficiency ? MAD is an enzyme of the purine nucleotide cycle, and an important role of this cycle could be the provision of tricarboxylic acid cycle intermediates, which would be important for optimal aerobic energy production [1,18,29,30]. Therefore it could be hypothesized that failure to provide sufficient tricarboxylic acid cycle intermediates in MAD-deficient muscle, particularly during the first 5-10 min of exercise when levels of these intermediates have been found to increase substantially in healthy muscle [31][32][33], would lead to a shift of energy production towards anaerobic sources and early fatigue.…”

Section: Discussionmentioning

confidence: 99%

Muscle function during repetitive moderate-intensity muscle contractions in myoadenylate deaminase-deficient Dutch subjects

¹

,

²

,

³

et al. 2002

Clinical Science

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We investigated whether the capacity for repetitive submaximal muscle contraction was reduced in a group of subjects (n=8) with a primary deficiency of myoadenylate deaminase (MAD). Quadriceps femoris muscle fatigue was evaluated using voluntary and electrically stimulated contractions during 20 min of repetitive voluntary isometric contractions at 40% of maximal force-generating capacity (MFGC). After 5 min of exercise, MFGC had declined significantly to 70.6+/-4.1% (mean+/-S.E.M.) and 87.2+/-1.6% of baseline values in MAD-deficient and sedentary control subjects (n=8) respectively (P=0.002 between groups). After 5 min of exercise, the half-relaxation time had increased significantly to 113.4+/-6.1% of baseline in MAD-deficient muscle, but had decreased significantly to 94.1+/-1.3% in control subjects (P=0.003 between groups). All control subjects completed the 20-min exercise test. Five of the MAD-deficient subjects had to stop exercising due to early muscle fatigue; however, three of the MAD-deficient subjects were able to complete the 20-min exercise test. In conclusion, although the capacity for repetitive submaximal isometric muscle contractions for the group of MAD-deficient subjects was significantly decreased, it remains uncertain whether MAD deficiency is the sole cause of pronounced muscle fatigue.

“…They observed a 53 % reduction in the accumulation of malate + fumarate compared with untreated control animals, and based on the difference in IMP accumulation between groups, calculated that the operation of the PNC accounted for at least 70% of the expansion of the TCAI pool during the first 10 min of contraction. In vitro studies have supported the potential role of the PNC as an anaplerotic process in skeletal muscle (Scislowski, Aleksandrowicz & Swierczynski, 1982). However, there is considerable controversy regarding the extent to which the PNC actually cycles in active muscle fibres (for review see Tullson & Terjung, 1991).…”

Section: Discussionmentioning

confidence: 99%

Anaplerotic processes in human skeletal muscle during brief dynamic exercise

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et al. 1997

The Journal of Physiology

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This study examined changes in tricarboxylic acid cycle intermediates (TCAIs) in human skeletal muscle during 5min of dynamic knee extensor exercise (∼80% of maximum workload) and following 2 min of recovery. The sum of the seven measured TCAIs (ΣTCAIs) increased from 1.10 ± 0.08mmol (kg dry weight)−1 at rest to 3.12 ± 0.24, 3.86 ± 0.35 and 4.33 ± 0.30 mmol (kg dry weight)−1after 1, 3 and 5 min of exercise, respectively (P≤ 0.05). The ΣTCAIs after 2 min of recovery (3.74 ± 0.43 mmol (kg dry weight)−1) was not different compared with 5 min of exercise. The rapid increase in ΣTCAIs during exercise was primarily mediated by large changes in succinate, malate and fumarate. These three intermediates accounted for > 90 % of the net increase in ΣTCAIs during the first minute of contraction. Intramuscular alanine increased after 1 min of exercise by an amount similar to the increase in the ΣTCAIs (2.33 mmol (kg dry weight)−1) (P≤ 0.05). Intramuscular pyruvate was also higher (P≤0.05) during exercise, while intramuscular glutamate decreased by ∼50% within 1 min and remained low despite an uptake from the circulation (P≤ 0.05). The calculated net release plus estimated muscle accumulation of ammonia after 1 min of exercise (∼60 μmol (kg wet weight)−1) indicated that only a minor portion of the increase in ΣTCAIs could have been mediated through the purine nucleotide cycle and/or glutamate dehydrogenase reaction. It is concluded that the close temporal relationship between the increase in ΣTCAIs and changes in glutamate, alanine and pyruvate metabolism suggests that the alanine amino‐transferase reaction is the most important anaplerotic process during the initial minutes of contraction in human skeletal muscle.

“…adenylosuccinate -fumarate + AMP) (Lowenstein, 1972). This cycle is postulated to fill an anaplerotic role in regulation of the levels of Krebs cycle intermediates entering at the malate level (Scislowski et al, 1982;Aragon and Lowenstein, 1980). The shared location of AMPda activity with the subsarcolemmal mitochondrial pool would facilitate such a role, particularly in the FOG fiber type.…”

mentioning

confidence: 97%

AMP deaminase histochemical activity and immunofluorescent isozyme localization in rat skeletal muscle.

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et al. 1992

J Histochem Cytochem.

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The cellular distribution of AMP deaminase (AMPda) isozymes was documented for rat soleus and plantaris muscles, utilizing immunofluorescence microscopy and immunoprecipitation methods. AMPda is a ubiquitous enzyme existing as three distinct isozymes, A, B and C, which were initially purified from skeletal muscle, liver (and kidney), and heart, respectively. AMPda-A is primarily concentrated subsarcolemmally and intermyofibrillarly within muscle cells, while isozymes B and C are concentrated within non-myofiber elements of muscle tissue. AMPda-B is principally associated with connective tissues surrounding neural elements and the muscle spindle capsule, and AMPda-C is predominantly associated with circulatory elements, such as arterial and venous walls, capillary endothelium, and red blood cells. These specific localizations, combined with documented differences in kinetic properties, suggest multiple functional roles for the AMPda isozymes or temporal segregation of similar AMPda functions. Linkage of the AMPda substrate with adenosine production pathways at the AMP level and the localization of isozyme-C in vascular tissue suggest a regulatory role in the microcirculation.

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