Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Earlier investigations involving chronic muscle stimulation have shown that skeletal muscle cells possess a much greater metabolic plasticity than had previously been recognized. We have described more fully the time course for the changes in different enzyme systems in single fibres of rabbit fast-twitch tibialis anterior (TA) muscles after periods of continuous stimulation of up to 10 weeks. After 2-5 wk every fibre shows higher levels of many oxidative enzymes than any control fibre; in some cases these levels are 2-10 times higher (well above any found even in the control soleus, a slow-twitch muscle). Citrate synthase, hexokinase and 3-oxoacid CoA-transferase are representatives of this group of enzymes. Other enzymes, such as malate dehydrogenase and amino acid aminotransferases also increase dramatically, but peak single fibre levels do not reach much above the highest in controls. These differential effects confirm at the single fibre level that chronic stimulation can alter mitochondrial composition. According to their staining reaction for myofibrillar ATPase, TA fibres are approximately 25% type IIA, and 75% type IIB, but by 5 wk these are converted to a mixture of type I, IIA and IIC fibres. At 5 wk, levels of glycolytic and high-energy phosphate transfer enzymes had decreased by 80% or more, and seemed to be adjusted to levels appropriate to their (new) ATPase type. This is in contrast to many enzymes of oxidative metabolism, which increase without synchronization with fibre type change. Determinations of metabolite concentrations in individual fibres from muscles freeze-clamped after varying periods of stimulation gave results which differ strikingly from data for acute stimulation. The findings reinforce our previous view that the high levels of ATP utilization engendered by chronic stimulation of muscle elicit a matching response in ATP production through a series of profound adaptations. Some of these are never encountered under the less extreme conditions of endurance exercise. Such features add to the interest and value of the chronic stimulation model as a means of studying the metabolic plasticity of muscle.
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PMID:Chronic stimulation of mammalian muscle: enzyme and metabolic changes in individual fibres. 252 28

Single fibers of rabbit fast-twitch tibialis anterior (TA) muscles were analyzed after continuous low-frequency stimulation for up to 8 wk. After 2-5 wk, every fiber showed higher levels of citrate synthase, hexokinase, and 3-oxoacid CoA-transferase than any control fiber; in some cases these levels were 2-10 times higher (well above any found even in the control soleus, a slow-twitch muscle). Average levels of malate dehydrogenase and alanine transaminase also rose dramatically, but peak single fiber levels were not much above the highest in controls. These differential effects confirm at the single fiber level that chronic stimulation can alter mitochondrial composition. Lactate dehydrogenase, fructose-bisphosphatase, and adenylate kinase declined to levels far below those of any control TA fiber, and, in the case of fructose-bisphosphatase, to within the activity range of control soleus fibers. According to their staining reaction for myofibrillar ATPase, TA fibers were initially 23% type IIA, and 74% type IIB, but by 5 wk these had been converted to a mixture of type I, IIA, and IIC fibers. At 5 wk, levels of lactate dehydrogenase, adenylate kinase, and malate dehydrogenase were characteristic of their (new) ATPase type, but 3-oxoacid CoA transferase had increased to levels 6-15 times higher than in control fibers of the same type.
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PMID:Chronic stimulation of mammalian muscle: enzyme changes in individual fibers. 302 Sep 91

The activities of citrate synthase, 3-oxoacid CoA-transferase, and Na/K-ATPase were determined in the proximal convoluted tubules (PCT) of midcortical nephrons from 16-, 21- and 30-day-old and adult rats. Enzyme microassays based on NAD amplification were run on tubule segments microdissected from lyophilized tissue sections, and the activities were expressed per unit of tissue dry weight. The activities of 3-oxoacid CoA-transferase (+ 155%) and citrate synthase (+ 44%) increased between 16 and 30 days, while no significant change in Na/K-ATPase activity occurred during this period. The results obtained in PCT from subcapsular nephrons were similar. It is concluded that active transport of Na+ coupled to mitochondrial ATP production might be mature in the PCT by the time of weaning, consistent with data on the development of Na+ reabsorption. Since adrenalectomy on day 16 induced no changes in the activities of oxidative enzymes or Na/K-ATPase on day 21 in midcortical or subcapsular PCT, the physiological rise in circulating glucocorticoids, characteristic of the weaning period, does not trigger the development of oxidative enzymes and Na/K-ATPase in the PCT of the developing rat kidney.
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PMID:Lack of control by adrenal steroids of oxidative enzymes and Na/K-ATPase development in the rat proximal tubule. 841 4

In the proximal convoluted tubule (PCT) of rat kidney, reabsorption is known to take place during fetal life, but no data on Na-K-ATPase and mitochondrial energy metabolism enzymes in this epithelium were available at fetal and neonatal stages. With use of the quantitative histochemistry approach, Na-K-ATPase, citrate synthase (tricarboxylic acid cycle), 3-ketoacid CoA-transferase and thiolase (ketone body oxidation), beta-hydroxyacyl-CoA dehydrogenase (fatty acid oxidation), and acetylcarnitine transferase (acetyl-CoA transport through mitochondrial membrane) were microassayed in PCT and metanephric mesenchyme of fetal and newborn rat kidney. The data indicate that, during fetal life, PCT differentiation involves concomitant increases in Na-K-ATPase and oxidative enzyme activities, supporting the hypothesis that mitochondria could play an active role in cellular ATP turnover when reabsorptive functions develop. Birth resulted in marked increases in the activities of Na-K-ATPase and of fatty acid and ketone body oxidation enzymes in the PCT, whereas no changes in enzyme activities occurred in the metanephric mesenchyme between the fetal and the newborn stage.
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PMID:Birth-related changes in energy metabolism enzymes and Na-K-ATPase in kidney proximal convoluted tubule cells. 912 12