Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study was undertaken to evaluate the relationship between physical performance capacity and the mitochondrial content of skeletal muscle. Four groups of rats were trained by means of treadmill running 5 days/wk for 13 wk. One group ran 10 min/day, a second group ran 30 min/day, a third group ran 60 min/day, and a fourth group ran 120 min/day. The magnitude of the exercise-induced adaptive increase in gastrocnemius muscle respiratory capacity varied over a twofold range in the four groups. There were significant correlations between the levels of three mitochondrial markers (cytochrome c, citrate synthase, respiratory capacity) in the animals' gastrocnemius muscles and the duration of a run to exhaustion. There was also a significant correlation between the amounts of glycogen remaining in liver and skeletal muscle after a 30-min-long exercise test and the respiratory capacity of the animal's leg muscles. These findings are compatible with the interpretation that a close relationshiop exists between skeletal muscle mitochondrial content and the capacity to perform endurance exercise.
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PMID:Skeletal muscle respiratory capacity, endurance, and glycogen utilization. 1816 Apr 57

The effects of thyroid hormone administration on the levels of a number of mitochondrial markers were measured in skeletal muscle and liver of normal rats. Injection of 18 mug of L-thyroxine (T4) per 100 g body wt every 4th day for 3 wk had no effect on the concentrations of cytochrome c, on citrate synthase activity, or on respiratory capacity of skeletal muscle. Injection of 200 mug of L-triiodothyronine (T3) daily for 5 days, or feeding 23 mg T4 and 7 mg T3/kg of diet for 2 wk, resulted in thyrotoxicosis and large increases in the activity of hepatic alpha-glycerophosphate dehydrogenase and other mitochondrial markers; however, the levels of activity of mitochondrial marker enzymes in gastrocnemius and quadriceps muscles were not significantly changed. Only when rats were fed 3 mg T4 and 1 mg T3/kg diet for a 6-wk period did we observe an increase in skeletal muscle mitochondrial markers. Thus, thyroxine treatment must be sufficiently prolonged if it is to be used as a tool for studying skeletal muscle mitochondrial biogenesis.
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PMID:Effects of thyroid hormone administration on skeletal muscle mitochondria. 16 30

The extent of skeletal muscle fiber type involvement during exercise training was evaluated by assessing the increase in oxidative markers in the muscles of rats trained by various exercise programs. Rats were trained by running 6 days/wk at 1 mph for 12 wk by one of four protocols: group I-10% grade, 2 h/day; group II-10% grade, 4 h/day; group III-30% grade, 40 min/day; and group IV-30% grade, 2 h/day. No distinction was found between the different programs for the increase in cytochrome c content or citrate synthase (CS) activity of mixed muscle. The more intense programs utilizing a 30% grade induced an increase in CS activity in the fast-twitch white (FTW) fiber that was twice that found in the 10% grade groups. The fast-twitch red (FTR) fibers of the 2 h/day or more groups showed a similar increase (90-95%) in CS activity except for the group that ran for only 40 min/day. These data suggest that: 1) running durations of moderately intense exercise longer than 2 h/day do not further increase the oxidative capacity of the working muscles; and 2) more intense exercise builds on the performance of previously used FTR fibers and additionally involves the low oxidative FTW fibers.
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PMID:Muscle fiber involvement during training of different intensities and durations. 17 89

To determine the effect of long-term thyrotoxicosis on muscle mitochondria, we measured representative mitochondrial enzymes from three different types of skeletal muscle (fast-twitch red and fast-twitch white from the quadriceps, and slow-twitch red from the soleus) in rats given 3 mg L-thyroxine and 1 mg triiodo-L-thyronine per kilogram of diet for 12 wk. Marker enzymes of the electron transport chain and citric acid cycle (cytochrome oxidase, cytochrome c, and citrate synthase) increase approximately twofold in soleus muscle in response to this treatment. The fast-twitch muscles exhibit no more than 44% increases in these enzymes in response to the same treatment. Relative to initial concentration, 3-hydroxybutyrate dehydrogenase increased to the same extent in fast-twitch red muscle as it did in the soleus (70%). Mitochondrial alpha-glycerophosphate dehydrogenase increased 76% in red quadriceps and 170% in soleus, but did not change in white muscle in the thyrotoxic rats. This differential sensitivity of the three types of muscle provides a tool for studying the mechanisms underlying the action of thyroid hormones on muscle mitochondria.
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PMID:Response of mitochondria of different types of skeletal muscle to thyrotoxicosis. 19 5

The hindlimbs of rats were immobilized, in plaster casts, for varying durations, and the time course for atrophy of muscle and of selected proteins in these muscles was determined. In those muscles whose lengths were at less than resting length during the fixation procedures, exponential decay to a new apparent steady state after atrophy was shown by wet and dry muscle weights and by the amounts of biuret protein, cytochrome c, and citrate synthase. The time taken to decrease to one-half of the final decrease at the new apparent steady state level was about 4-6 days for the above parameters which decayed exponentially. In contrast, the myoglobin concentration increased during atrophy and the amount of myoglobin remain unchanged during atrophy. When fixation procedures on limbs were such that muscles were stretched to lengths greater than resting length, then the onset of atrophy was delayed; indeed, in some cases muscles hypertrophied when fixed in the stretched position.
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PMID:Time course of muscular atrophy during immobilization of hindlimbs in rats. 19 96

Citrate synthase and cytochrome c increase in soleus muscle of rats in response to excess thyroid hormones. The half times of the increase in the levels of citrate synthase and cytochrome c in soleus muscle during induction are greater than the half times of the decline in enzyme levels after cessation of treatment (15 days vs. 7 days for citrate synthase). Denervation of the soleus does not prevent the increase in citrate synthase in response to thyrotoxicosis. This provides evidence that thyroid hormones affect the muscle directly and not via the motor nerves. ATP concentration is reduced in liver, but not in soleus muscle in response to thyrotoxicosis. Creatine phosphate is not significantly altered in soleus muscle. Cyclic AMP is slightly lower in thyrotoxic soleus muscle. Simultaneous treatment with thyroid hormones and propranolol does not affect the increase in citrate synthase in response to excess thyroid hormones. It is concluded that the increase in muscle mitochondria associated with thyrotoxicosis is not mediated via the nervous system or by a cAMP-regulated process.
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PMID:Time course of the T3- and T4-induced increase in rat soleus muscle mitochondria. 21 61

The effects of thyroid deficiency (Td) and of chemical sympathectomy (Sx) were studied on marker enzymes of energy metabolism in cardiac muscle of neonatal and of adult rats. Td prevented the normal development of neonatal body weight, relative heart mass, and cardiac levels of cytochrome c (-22%), citrate synthase (-27%), phosphofructokinase (-20%) and Mg2+- and Ca2+-ATPase activity of purified myofibrils (-33%, -44%). Exogenous thyroxin replacement restored those parameters studied to normal with the exception that it persistently elevated citrate synthase activity significantly above normal control levels. Responses similar to those of Td neonates occurred when adult rats were similarly treated. Sx produced no consistent effects on respiratory and glycogenolytic marker enzymes, but caused a 20% reduction in Ca2+-ATPase activity of both neonatal and adult cardiac myofibrils. These findings suggest that cardiac muscle cells require thyroxin for normal growth and enzyme development. Also, Sx may impair cardiac functional capacity by altering Ca2+ activity of actomyosin ATPase.
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PMID:Effects of thyroid deficiency and sympathectomy on cardiac enzymes. 21 2

Expression of the rate-limiting heme biosynthetic enzyme 5'-aminolevulinate synthase (ALAS) was investigated in skeletal muscle of 3-wk-old rats fed an iron-deficient diet. After 14 days, ALAS activity had declined 70% relative to control (2.1 +/- 0.2 vs. 0.6 +/- 0.1 nmol.h-1.g-1; P less than 0.005). Similar decreases were observed for blood hemoglobin (11.4 +/- 0.2 vs. 3.9 +/- 0.3 g/dl; P less than 0.005) and muscle cytochrome c (14.5 +/- 1.3 vs. 7.1 +/- 0.6 nmol/g; P less than 0.005). An iron-deficient diet decreased body and skeletal muscle growth by 15 (P less than 0.005) and 10% (P less than 0.05), respectively, whereas concentrations of protein, RNA, ALAS mRNA, and citrate synthase activity in muscle were not different from control. One mechanism by which heme biosynthesis may be slowed in muscle of young anemic rats is a decrease in ALAS activity. At a time when enzyme activity was decreased, ALAS mRNA expression was not affected by an iron-deficient diet, suggesting that steps after transcription of the ALAS gene may regulate the decrease in activity.
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PMID:5'-Aminolevulinate synthase activity is decreased in skeletal muscle of anemic rats. 132 16

The effect of chronic left ventricular pressure overload on the activities of mitochondrial respiratory chain enzymes was investigated in myocardial biopsies from the left ventricular apex of 13 patients undergoing aortic valve replacement for aortic valve stenosis. Transvalvular pressure gradients measured by left-sided heart catheterization ranged from 52 to 100 mmHg. The specific activity of mitochondrial respiratory chain enzyme complexes I+III (antimycin A sensitive NADH cytochrome c oxidoreductase) and the myocardial concentrations of coenzyme Q10 (CoQ10) increased significantly (P < 0.05) with increasing aortic valve pressure gradient. In contrast, the specific activities of complex IV (cytochrome c oxidase), succinate dehydrogenase, and citrate synthase, a mitochondrial matrix enzyme, showed no significant correlation with the pressure gradient. Since CoQ10 is the rate-limiting compound of the activity of complexes I+III but not of cytochrome c oxidase, succinate dehydrogenase, or citrate synthase, these data suggest that the increase in the activity of complexes I+III is due to the increase in CoQ10 content.
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PMID:Positive correlation between aortic valve pressure gradient and mitochondrial respiratory chain capacity in hypertrophied human left ventricle. 145 Jun 14

Quadriceps muscle specimens from autopsy of 28 neonates (gestational age 25-42 weeks) were investigated to determine pyruvate and malate oxidation rates and several enzymes of the mitochondrial oxidative process. In general, the levels of all mitochondrial parameters measured, including carnitine levels, were lower in the neonates who died within the first week of life than those in the control group (age > 5 years). Pyruvate and malate oxidation rates (P < 0.05), activities of pyruvate dehydrogenase complex (P < 0.10) and succinate: cytochrome c oxidoreductase (P < 0.05) increased significantly with gestational age. Pyruvate oxidation rates (P < 0.05) as well as activities of citrate synthase (P < 0.05) and NADH:Q1 oxidoreductase (P < 0.05) were significantly lower in the group of very preterm infants at an age of 1-7 days compared with very preterm infants at an age between 3-8 weeks. We conclude from our study that special reference values are necessary for a correct biochemical diagnosis of mitochondrial encephalomyopathies in the neonatal period. Differences between preterm and fullterm children of the same age (1 week) indicate a maturational process in human muscle tissue during gestation. Comparison of two different age groups within the very preterm neonates point to a postnatal maturation of the mitochondrial energy metabolism, at least in preterm neonates.
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PMID:Enzyme activities of the mitochondrial energy generating system in skeletal muscle tissue of preterm and fullterm neonates. 148 60


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