Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The metabolic effects on rat cardiac and skeletal muscle of a strenous program of swimming, of cold acclimation and of isoprenaline treatment (0.3 mg/kg daily for 5 five-day weeks) were compared. Exercised and cold-exposed rats gained less body weight than did controls or isoprenaline-treated rats. In all treated groups the heart and the intercapular brown adipose tissue hypertrophied. The size of the adrenals increased only in isoprenaline-treated animals. Cold-acclimation and physical training increased and isoprenaline treatment reduced or did not affect the activities of succinate dehydrogenase, malate dehydrogenase and citrate synthase of cardiac muscle. In the skeletal muscle all treatments resulted in increased activities of these enzymes. Of the anaerobic enzymes analysed, only the activity of hexokinase increased in response to the treatements used. This increase was the same in cardiac as in skeletal muscle, but it was significantly greater with isoprenaline-treatment than with training or with cold-acclimation. The activities of lactate dehydrogenase and phosphofructokinase did not differ significantly. All treatments improved cold resistance, but only swimming exercise and cold acclimation significantly increased tolerance to exercise. It is concluded that prolonged stimulation of adrenergic beta-receptors by catecholamines is responsible for the metabolic changes observed.
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PMID:Comparison of the effects of physical exercise, cold acclimation and repeated injections of isoprenaline on rat muscle enzymes. 12 87

Rats were treated by daily alprenolol (10, 20 and 50 mg/kg) injections for 5 days a week for 4 weeks. At 20--21 degrees C alprenolol treatment retarded the weight gain of the animals and increased the weight of the adrenals. These changes were not seen at 29 degrees C. The reduction in size and fat content of the interscapular brovin adipose tissue in drug-treated rats was independent of experimental temperature. At 20--21 degrees C prolonged beta-blockade did not cause any changes in the enzymes of the energy metabolism. At 29 degrees C, however, alprenolol treatment antagonized the decrease in activity of oxidative enzymes (succinate dehydrogenase, malate dehydrogenase, citrate synthase) and the decrease in protein concentration of the cardiac muscle. In skeletal muscle alprenolol treatment significantly decreased the activities of oxidative enzymes and antagonized the rise in the activity of lactate dehydrogenase resulting from warm acclimation. The increased activities of oxidative enzymes in interscapular brown adipose tissue of aprenolol treated rats were coupled with an increase in protein concentration of the tissue. Although these changes were more marked at 29 degree C they were observable at 20--21 degree C, too. The difference in the drug effects at 20--21 degrees C and 29 degrees C can be accounted for by the compensatory catecholamine release at the lower temperature, due to impaired thermoregulatory capacity after alprenolol. Prolonged beta blockade decreased the exercise tolerance and cold tolerance of the rats. An increased response of the diastolic blood pressure to an alpha-adrenergic drug, noradrenaline, and a decreased response to a beta-adrenergic drug, isoprenaline, in alprenolol-treated rats indicates a shift from beta- to alpha-receptors.
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PMID:Effect of prolonged beta-blockade on energy metabolism and adrenergic responses in the rat. 59 3

This investigation evaluated the hypothesis that the age-related decline in cold-induced thermogenesis observed in male (F344) rats is associated with altered substrate concentrations of glucose, lactate, and/or liver and muscle glycogen. Body mass-independent O2 consumption, core temperature, and serum glucose and lactate concentrations were measured at rest and during 4 h of exposure to 5 degrees C in male F344 rats ages 6, 12, and 26 months. At the end of the 4-h cold exposure, liver, soleus, and gastrocnemius tissues were removed, frozen, and analyzed for glycogen concentration and/or citrate synthase activity. Core temperature decreased during cold exposure and was consistently less in the 26-month versus the 6- and 12-month rats. There were no significant differences between the 6- and 12-month-old rats with respect to cold-induced O2 consumption, but measures were significantly lower in the 26-month-old rats. During cold exposure, serum lactate and glucose concentrations increased in the 26-month-old animals compared to those in the 6- and 12-month-old rats, while liver glycogen concentrations decreased in all groups, and gastrocnemius glycogen contents decreased in the 12- and 26-month-old rats. Citrate synthase specific activity (mumol.[min.microgram.protein] -1) did not differ with age. These data suggest that carbohydrate availability (as measured by serum glucose and muscle glycogen) is not a limiting factor in the attenuated cold-exposed thermogenic response of the 26-month-old male F344 rat. However, it appears that the 26-month-old rat may have a diminished capacity to fully oxidize carbohydrate during cold exposure.
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PMID:Effect of cold on serum substrate and glycogen concentration in young and old Fischer 344 rats. 152 93

1. Responses of enzymic characteristics of gastrocnemius muscle were studied when frogs (Rana pipiens) were exposed to cold environment (4 degrees C). 2. The content of adenosine triphosphate (ATP) decreased significantly after cold exposure. This decrease was greater in starved than in fed frogs. 3. Although the glycogen content did not change, lactate levels were lower in cold-exposed than room-temperature (control) frogs. No change was observed in glycogen and lactate between fed and unfed frogs kept at 4 degrees C for 2 months. Lactate dehydrogenase activity tended to increase during chronic cold exposure, but not significantly. 4. The activities of citrate synthase, cytochrome oxidase, and beta-hydroxyacyl CoA dehydrogenase were higher in gastrocnemius of chronically cold-exposed frogs than in room-temperature controls. This increase was statistically significant only in the muscles of starved frogs; these muscles had the greatest decrease in ATP. 5. It was suggested that chronic cold exposure decreases skeletal muscle ATP content but may not affect glycolysis. The data also suggested that the decrease in ATP content stimulates mitochondrial biogenesis which increases enzyme activities.
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PMID:Effects of exposure to cold on metabolic characteristics in gastrocnemius muscle of frog (Rana pipiens). 326 90

Inter- and subscapular brown adipose tissue depots were removed from nine female Osborne-Mendel rats. These lipectomized animals and nine sham-operated controls recovered from surgery for 7 days at 25 degrees C and were then placed on a highly palatable liquid diet. All animals were maintained for a 2nd wk at 25 degrees C before being switched to 8 degrees C. After 9 wk in the cold, animals were killed, and the brown adipose tissue was dissected from scapular, cervical, thoracic, perirenal, and axillary regions. Total brown fat pad mass, protein content, brown adipocyte number, citrate synthase activity, and beta-hydroxyacyl CoA dehydrogenase activity in each of the dissected brown fat depots were significantly less than those of the sham-operated controls. Thus there was incomplete metabolic compensation in the remaining brown fat depots after the removal of the scapular brown fat in the lipectomized rats. The mass and lipid content of the retroperitoneal white adipose depot were significantly increased in the lipectomized rats as was their carcass fat content (up 14%). Food intake of the lipectomized rats was slightly but significantly decreased. These data indicate that a reduction in the amount of functional brown fat is accompanied by increased body fat accretion and are thus consistent with the hypothesis that decreased brown adipose thermogenesis can lead to altered energy balance and increased white fat deposition.
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PMID:Brown adipose tissue lipectomy leads to increased fat deposition in Osborne-Mendel rats. 397 Feb 38

Common carp (Cyprinus carpio L.), 1 kg body weight, were acclimated for 1-2 months to water temperatures of either 7-8 degrees C (cold-acclimated group) or 23-24 degrees C (warm-acclimated group). Single fast fibres and small bundles of slow fibres were isolated from the myotomal muscles and chemically skinned. Force-velocity (P-V) characteristics were determined at 7 degrees C and 23 degrees C. The contractile properties of carp muscle fibres are dependent on acclimation temperature. In the warm-acclimated group maximum isometric tensions (P0, kN m-2) are 47 +/- 6 and 64 +/- 5 for slow muscle fibres and 76 +/- 10 and 209 +/- 21 for fast muscle fibres at 7 degrees C and 23 degrees C, respectively. Maximum contraction velocities (Vmax, muscle lengths-1), are 0.4 +/- 0.05 and 1.5 +/- 0.1 at 7 degrees C (slow fibres) and 0.6 +/- 0.04 and 1.9 +/- 0.4 at 23 degrees C (fast fibres). All values represent mean +/- S.E. P0 and Vmax at 7 degrees C are around 1.5-2.0 times higher for slow and fast muscle fibres isolated from the cold-acclimated group. Fibres from 7 degrees C-acclimated carp fail to relax completely following maximal activations at 23 degrees C. The resulting Ca-insensitive force component (50-70% P0) is associated with the development of abnormal crossbridge linkages and very slow contraction velocities. Activities of enzymes associated with energy metabolism were determined at a common temperature of 15 degrees C. Marker enzymes of the electron transport system (cytochrome oxidase), citric acid cycle (citrate synthase), fatty acid metabolism (carnitine palmitoyl transferase, beta-hydroxyacyl CoA dehydrogenase) and aerobic glucose utilization (hexokinase) have 30-60% higher activities in slow muscle from cold-acclimated than from warm-acclimated fish. Activities of cytochrome oxidase and citrate synthase in fast muscle are also elevated following acclimation to low temperature. It is concluded that thermal compensation of mechanical power output by carp skeletal muscle is matched by a concomitant increase in the potential to supply aerobically-generated ATP at low temperatures.
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PMID:Force-velocity characteristics and metabolism of carp muscle fibres following temperature acclimation. 409 57

Concentration of ([Glc]) and turnover (Ro) of plasma glucose, concentration of free fatty acids in plasma ([FFA]), and concentration of glycogen in muscle and liver were measured in freshly captured summer- and winter-acclimatized American goldfinches (Carduelis tristis). These birds were acutely exposed to one of three thermal regimes: 1) "thermoneutral," 30 degrees C in air, 2) "cold," -15 degrees C in air, and 3) "severe cold," 0 degrees C in 79% He and 21% O2. Additionally, the activities of citrate synthase (CS), phosphofructokinase (PFK), and beta-hydroxyacyl-CoA dehydrogenase (HOAD) were measured in pectoralis and leg muscles of winter and summer birds. Ro for goldfinches at 30 degrees C is unchanged between winter and summer, whereas it is 25% lower at -15 degrees C in winter than in summer birds, even though rates of heat production are similar. Additionally, winter animals depleted muscle glycogen at slower rates than summer individuals when exposed to "cold" or "severe cold." [Glc] and [FFA] for each test regime did not vary between seasons. The activity of the beta-oxidative enzyme HOAD is the pectoralis muscle (the main thermogenic tissue) increases by 50% from summer to winter, but the activities of PFK and CS remain essentially constant. We conclude that the ability to restrict carbohydrate use under cold stress is a component of the winter acclimatization process in the American goldfinch. One mechanism which might foster this ability in the increase in beta-oxidative capacity of the flight muscles, permitting a greater reliance on fatty acids by winter animals during cold-induced thermogenesis.
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PMID:Substrate metabolism in seasonally acclimatized American goldfinches. 621 Nov 5

During seasonal acclimatization in white-footed mice (Peromyscus leucopus), there is a substantial increase in the capacity for aerobic heat production under cold stress (Mmax) in winter animals. The possibility that increases in levels of enzymes involved in aerobic heat production could be responsible for the increase in Mmax was investigated in mice captured in summer and winter. Activities of citrate synthase (CS) and beta-hydroxyacyl-CoA dehydrogenase (HOAD) and concentrations of cytochrome c (cyt c) were measured in the two primary thermogenic tissues of small mammals, skeletal muscle and brown adipose tissue (BAT). Additionally, cyt c was measured in heart, liver, and whole-body samples. CS and cyt c were used as indicators of aerobic capacity, and HOAD was used to indicate the capacity for beta-oxidation. In winter CS, cyt c, and HOAD increased (expressed per g wet mass) in skeletal muscle and BAT. There was an increase in cyt c of whole-body samples, liver, and skeletal muscle of between 55 and 78%, but no change was observed in cardiac tissue. There was an approximately 80% increase in CS and HOAD in skeletal muscle. The highly aerobic nature of BAT and its primary role in heat production are supported by the high activities in summer animals and the increase observed in winter (200, 1,570, and 220% increase in CS, HOAD, and cyt c, respectively).
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PMID:Seasonal changes in enzymes of aerobic heat production in the white-footed mouse. 626 12

To investigate the contribution of brown fat (BAT) to the development of obesity in genetically obese Zucker rats (fa/fa), scapular brown fat (SBAT) was removed from obese and lean 4-wk-old females. Eight weeks after surgery there was no regrowth of SBAT. Lipectomy had no effect on body weight gain, food intake, and body composition when rats were housed at 25 degrees C. Lean rats completely compensated for the lipectomy by increasing BAT mass, protein, cellularity, and activity of citrate synthase (CS) in axillary, perirenal, and thoracic depots. beta-Hydroxyacyl-coenzyme A dehydrogenase (HOAD) activity was increased, but compensation was incomplete. In lipectomized obese rats, only BAT protein and cell number were increased sufficiently for complete compensation. In a second experiment SBAT was removed from obese and lean rats, but rats were housed in the cold (10 degrees C) for 8 wk. In lean rats, although compensation was incomplete, it was sufficient to maintain a weight gain and body composition comparable with sham-operated lean rats. In obese rats, where there was little or no compensation for lipectomy, weight gain and fat deposition were greater than observed in sham-operated obese controls. These data support the hypothesis that reducing the amount of functional BAT contributes to the development of increased adiposity.
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PMID:Scapular brown fat removal enhances development of adiposity in cold-exposed obese Zucker rats. 649 75

Older male Fischer 344 (F344) rats do not maintain core temperature as well as do older females during cold exposure. To elucidate factors contributing to the decreased thermoregulatory ability of older males, the metabolic potentials of interscapular brown adipose tissue (IBAT) and skeletal muscle were evaluated at rest (26 degrees C) and during 4 h of cold (6 degrees C) in male and female F344 rats, aged 6, 12, and 26 mo. Compared with 26-mo-old females, cold-exposed 26-mo-old males exhibited a greater drop in core temperature and lower amounts of IBAT mitochondrial uncoupling protein (UCP) and IBAT thyroxine 5'-deiodinase (T5'D) activity. Unlike females, 26-mo-old males showed no cold-induced increase in total IBAT UCP or T5'D activity. In contrast, plasma norepinephrine was higher in cold-exposed 26-mo-old males vs. females, whereas plasma insulin and thyroxine did not differ with gender. Skeletal muscle oxidative capacity (measured by citrate synthase activity) and carbohydrate availability (measured by muscle glycogen and plasma glucose levels) did not differ between the 26-mo-old males and females. Our data suggest that altered regulation of IBAT UCP levels during cold exposure of aged rats, due at least in part to attenuated cold-induced IBAT T5'D activity, contributes to the gender difference in thermoregulatory ability of older males vs. females.
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PMID:Effects of age and gender on brown fat and skeletal muscle metabolic responses to cold in F344 rats. 773 4


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