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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sarcolemmal preparations isolated from rat and guinea pig hearts mostly consisting of inside-out membrane vesicles catalyzed ATP-dependent Ca2+ accumulation. The creatine kinase ATP-regenerating system containing exogenous creatine kinase and phosphocreatine was most effective in supporting Ca2+ accumulation. The normalized rate of Ca2+ accumulation obtained by dividing the Ca2+ uptake rate by its initial equilibrium vesicular content was correlated with the (Na+ K+)-ATPase activity. The ATP-dependent Ca2+ uptake in sarcolemmal vesicles was inhibited by cardenolids--digitoxigenin and ouabain (40-50%), when the latter acted from inside the vesicles. The Ca2+ gradient formed in sarcolemmal vesicles at the expense of ATP was dissipated by Na+ but not by Li+ added into the external medium. The external sodium ions also caused Ca2+ efflux from sarcolemmal vesicles equilibrated with Ca2+. The described effects of Na+ are taken to show the existence of a Na-Ca exchange system in cardiac sarcolemma. Ca2+-ATPase of sarcoplasmic reticulum (SR) vesicles from guinea pig heart as well as ATP-dependent Ca2+ influx in these preparations were found to be partially suppressed by digitoxigenin. External NaCl led to be a rapid (during 5-10 sec) fall in vesicular Ca2+ content (by about 40%) accumulated at the expense of ATP followed by a return of Ca2+ content to its initial level. LiCl had no effect on Ca2+ content in SR. NaCl gradient directed inside the SR vesicles did not influence the distribution of Ca2+ between internal and external vesicular volumes in equilibrium (without ATP). The differences in properties of the Ca-pump of sarcolemma and sarcoplasmic reticulum found in this work support the idea on the existence of sarcolemmal system of ATP-dependent transport of Ca2+.
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PMID:[Effect of cardenolids and sodium ion gradient on ATP-dependent Ca2+ accumulation in cardiac sarcolemmal vesicles]. 627 79

Vesicular sarcolemmal preparations isolated from rat hearts were characterized by high total ATPase (4.32 +/- 0.57 mumol/min per mg), adenylate cyclase (121 +/- 11 pmol/min per mg) and creatine kinase (1.73 +/- 0.35 mumol/min per mg) activities as well as Na-Ca exchange specific to sodium. ATPase activity was inhibited with digitoxigenin by 50-70% and was not changed by ouabain, ionophore A23187 or oligomycin. Sarcolemmal vesicles bound [3H]digitoxigenin and [3H]ouabain in isotonic medium in the presence of Pi and Mg2+. The number of binding sites for hydrophobic digitoxigenin (N = 237 pmol/mg) was several-times higher than that for hydrophilic ouabain (N = 32.7 pmol/mg). These data show that sarcolemmal preparations were not significantly contaminated by mitochondria and sarcoplasmic reticulum and consisted mostly of inside-out vesicles. Incubation of these vesicles with 45Ca2+ (0.5-10 mM) led to penetration of the latter into the vesicles with the following binding characteristics: number of binding sites (N = 20.5 +/- 4.6 nmol/mg, Kd approximately equal to 2.0 mM). Ca2+ binding to the inner surface of vesicles was proved by the following facts: (1) Ca2+ ionophore A23187 increased slightly total intravesicular Ca2+ content but markedly accelerated Ca2+ efflux along its concentration gradient; (2) gramicidin and osmotic shock showed a similar accelerating effect. Ca2+ efflux from the vesicles along its concentration gradient ([Ca2+]i/[Ca2+]e = 2.0 mM/0.1 microM) was inhibited by Mn2+, Co2+, and verapamil when they acted inside the vesicles. The rate of Ca2+ efflux was hyperbolically dependent on intravesicular Ca2+ concentration (Km approximately equal to 2.9 mM). These data reveal that Ca2+ efflux from sarcolemmal vesicles is controlled by Ca2+ binding to the sarcolemmal membrane. Ca2+ efflux from the vesicles was stimulated 1.7--times after incubation of vesicles with 0.2 mM MgATP or MgADP and 15-times after treatment with 0.2 mM adenylyl beta, gamma-imidodiphosphate. Enhancement in the rate of Ca2+ efflux correlated with the increase in the intravesicular Ca2+ content. ATP-stimulated Ca2+ efflux was suppressed by verapamil and was nonmonotonically dependent upon the transmembrane potential created by the K+ concentration gradient in the presence of valinomycin, Ca2+ efflux being slower at extreme values of membrane potential (+/- 80 mV).
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PMID:Mechanism of passive Ca2+ permeability of vesicular sarcolemmal preparations from rat hearts. 629 43

Sarcolemmal preparations from rat and guinea pig cardiac muscle consisting mostly of inside-out vesicles were found to accumulate Ca2+ in the presence of ATP. The normalized rate of calcium uptake (the rate of calcium accumulation divided by its initial content in vesicles) correlated with the Na+ -K+ ATPase activity of the preparation. ATP-dependent calcium uptake by sarcolemmal vesicles was inhibited by 40-50% by cardenolids, digitoxigenin and ouabain, when the latter was included inside the vesicles. The Ca2+ gradient formed in the presence of ATP was dissipated by the addition of external sodium; Li+ was found to be ineffective in this process. External sodium also caused calcium release from vesicles pre-equilibrated with calcium in the medium. In the energy-dependent calcium uptake, the membrane-bound creatine kinase ATP-regenerating system was found to be the most effective energy source for active calcium transport. The results obtained may be interpreted to show that either the cardiac sarcolemma contains an energy-dependent calcium transport system or the sarcolemmal Na+ -K+ ATPase is able to transport calcium instead of sodium.
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PMID:Is the sarcolemmal Na+ -K+ ATPase involved in active calcium transport? 630 78

Experiments were carried out to test the hypothesis that membrane injury associated with Ca2+ depletion of the heart is involved in the development of Ca2+ overload during the Ca2+ paradox phenomenon. Biochemical properties of sarcolemma (SL) and sarcoplasmic reticulum (SR) isolated from the rabbit heart after 10 min of Ca2+-free perfusion were examined. This treatment predisposes hearts to the Ca2+ paradox as assessed by perfusate creatine kinase (CK) activity and heart contractility during reperfusion with Ca2+. Homogenates prepared from Ca2+ depleted heart were examined for their capacity to accumulate Ca2+ in the presence of ATP, which is mainly a property of the SR Ca2+ pump. The initial rate of Ca2+ pumping was 55% less in the Ca2+ depleted heart. The activities of 5'-nucleotidase, Na+/K+-ATPase and Na+/Ca2+ antiporter, and the Ca2+ permeability were studied in isolated SL vesicles. Na+/K+-ATPase activity was 75% less in SL isolated from Ca2+ depleted hearts, no significant changes were observed with the other parameters studied. Calmodulin (CaM) content in SL, assayed by radioimmunoassay, was unchanged. However, a 98% increase was observed in homogenates prepared from Ca2+ depleted hearts. The possible involvement of CaM in the Ca2+ paradox phenomenon is discussed. The data provide evidence that the net Ca2+ gain of myocardial cells in Ca2+ repletion may in part be associated with a loss of the ability of the SL and SR to remove Ca2+ from the cytosol.
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PMID:Diminished Na+/K+ and Ca2+ pump activities in the Ca2+ depleted heart: possible role in the development of Ca2+ overload during the Ca2+ paradox. 631 44

Changes of the extra- and intramitochondrial ATP/ADP ratios as a function of the respiratory state were measured in incubations with rat liver mitochondria. ATPase or creatine/creatine kinase was used to change the extramitochondrial ATP/ADP ratio; the separation of the mitochondrial pellet was performed by a Millipore filtration technique. Under all conditions tested, the intramitochondrial ratio changed in the same direction as the extramitochondrial one, except in the presence of atractylate where this correlation was not observed. Furthermore, it could be shown that the oxygen uptake and pyruvate carboxylase activity correlated with the intramitochondrial ATP/ADP ratio and not with the extramitochondrial one. These results do not support the proposal that the adenine nucleotide translocase is rate limiting for respiration.
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PMID:Relation between extra- and intramitochondrial ATP/ADP ratios in rat liver mitochondria. 644 52

After the intraperitoneal administration of 0.5 mEq 134 CsCI . kg -1 to mice, the maximum cesium level in the kidney's, heart, lungs and liver was found in the first hour (T 1/2 13 h), in the muscles after 8 h (T 1/2 180 h), in the brain after 24 h (T 1/2 140 h) and in the blood after 24 h. Maximum cesium levels were found in the muscles. Rats excreted about 17% of the administered dose in 24 h and 38% in 144 h. Most of the cesium (about 90%) is excreted in the urine. In rats, equalization of the plasma and RBC cesium levels takes longer than 6h. Cesium transport is not entirely dependent on the ATPase system, as shown by the results given by the crude mitochondrial fraction with a reduced potassium content. Among the various univalent ions studied, the effect of cesium on creatine kinase, 5'-nucleotidase, phosphodiesterase and deaminase activity was the smallest.
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PMID:Distribution of cesium in the organism and its effect on the nucleotide metabolism enzymes. 645 57

Vesicular preparations of sarcolemma isolated from rat myocardium possessed high ATPase (4.32 +/0 0.57 micromole/min per mg), adenylate cyclase (121 +/- 11 pmole/min per mg) and creatine kinase (1.74 +/- 0.35 micromole/min per mg) activities and a Na-Ca exchange activity specific for sodium. The ATPase activity was inhibited by digitoxigenin by 50-70% and was not changed by ouabain, EGTA, ionophore A23187 and oligomycin, thus showing the absence of mitochondrial and sarcoplasmic reticulum contaminations in the sarcolemmal preparations. The preparations consisted mostly of closed inside-out vesicles. The preparation was used to study the mechanism of Ca2+ penetration across the sarcolemmal membrane. For this purpose the vesicles were load with 45Ca2+, which relatively slowly diffused from the medium into the vesicles, and which was bound to the binding sites inside the vesicles (n = 20.5 +/- 4.6 nmoles per mg of protein, Kd approximately equal to 1.8 +/- 0.21 mM). The transmembrane movement of Ca2+ was demonstrated by the following findings: 1) the ionophore A23187 only insignificantly increased the total vesicular Ca2+ content, but strongly accelerated Ca2+ efflux from the vesicles along its concentration gradient; 2) gramicidin and osmotic shock caused a similar acceleration of Ca2+ efflux. Ca2+ efflux from these vesicles along Ca2+ concentration gradient was studied under conditions, when the extravesicular Ca2+ content was lowered due to its binding to EGTA and by dilution. The gradient of Ca2+ concentration was from 2.0 mM inside to approximately 0.1 micro M outside. The rate of 45Ca2+ efflux depended hyperbolically on the intravesicular Ca2+ efflux from the vesicles was inhibited by Mn2+, Co2+ and verapamil when they acted from the inside of the vesicles. An increase in ionophore A23187 concentration increased the efflux of Ca2+ hyperbolically and enhanced only the maximal rate of the efflux. It is concluded that the passive permeability of Ca2+ across the sarcolemmal membrane along its concentration gradient is controlled by Ca2+ binding to the membrane.
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PMID:[Passive Ca2+ permeability of vesicular sarcolemmal preparations from myocardium]. 645 35

Skeletal limb muscles of the dog could generally be differentiated into three fibre types according to myosin adenosine triphosphatase (ATPase) (pH 9.4) and succinic dehydrogenase activities. However, because this was not always possible, for comparative purposes only, division into low myosin ATPase (slow twitch) type I and high myosin ATPase (fast twitch) type II fibres was used. The percentage of these fibre types in m deltoideus, m triceps brachii caput longum, m vastus lateralis, m gluteus medius, m biceps femoris and m semitendinosus was examined in the greyhound, crossbred and foxhound. In all muscles the greyhound had a significantly higher percentage of fibres with high myosin ATPase activity at pH 9.4 than the other breeds, with almost 100 per cent in most muscles examined. The activities of nine enzymes and glycogen concentration were determined in m gluteus medius and m semitendinosus of the greyhound and crossbred. Significantly higher levels of creatine kinase, aldolase, alanine aminotransferase and citrate synthase and significantly lower activities of 3-hydroxyacyl coenzyme A dehydrogenase and hexokinase were found in both muscles of the greyhound. The implications of these findings are discussed.
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PMID:Skeletal muscle fibre composition in the dog and its relationship to athletic ability. 645 29

The present study ascertained the influence of litter-size-induced perinatal nutritional modification on cardiac contractile protein enzymatic activity and isomyosin composition. Myofibrillar enzyme activities for Mg2+ -ATPase, Ca2+ -ATPase, and creatine kinase (CK) in the weanling heart were unaltered by nutritional modification. However, these enzyme activities were all significantly augmented in the adult heart. Hill plot analyses of Mg2+ -ATPase activities indicated that myofibrillar calcium regulation was not influenced by either nutritional modification or the weanling-to-adult developmental progression. Isomyosin V1 composition (90 +/- 1%) correlated with plasma thyroid hormone level in normal-growth (8/litter) weanlings. Undernutrition retarded conversion of V3 isomyosin to the V1 species while overnutrition enhanced isomyosin conversion. Isomyosin composition in weanling rats subjected to perinatal nutritional modification was independent of thyroid status. In the adult rat, plasma thyroxine levels were increased, whereas V1 isomyosin remained unchanged (88 +/- 2%) compared with that of the weanling groups. Discrepancies in the relationship between contractile protein enzymatic activities, myosin composition, and heart function are apparent between both the litter-size-adjusted weanling rats and between weanling and adult animals. These discrepancies indicate the complex relationship between heart function and contractile protein properties.
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PMID:Perinatal nutritional modification of weanling rat heart contractile protein. 650 43

In 13 rabbits the rectus femoris muscle was freely transplanted from the left to the right side using microneurovascular anastomoses. About 7 months after surgery the muscle transplants were assessed functionally by force measurements. On the average, the transplanted muscles regained 55 percent of the maximal tetanic tension of unoperated, normal rectus femoris muscles, expressed as force per gram of muscle weight even 68 percent. After functional assessment, the muscles were weighed and then used for histologic, histochemical, planimetric, and biochemical evaluation. H&E-stained cross sections showed a high content of healthy muscle fibers; only some small atrophic and single fat cells were scattered over the cross sections. Good reinnervation over the sutured muscle nerve was confirmed by the type-grouping of muscle fibers in the NADH and myofibrillar ATPase staining. There was an excellent correlation between the functional results and the histologic picture as well as the content of choline acetyltransferase (CAT). A certain parallelism was found between the function of the transplants and the content of hexokinase, but none for the other estimated muscle enzymes, such as malate dehydrogenase (MDH), creatine kinase (CK), and lactic dehydrogenase (LDH). All enzyme levels were lower than in normal muscles. The results of this experimental series underline the utility of muscle transplantation with microneurovascular anastomoses to restore lost muscle function, even in the extremities, when strong forces are needed.
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PMID:Experimental free-muscle transplantation with microneurovascular anastomoses. 683 65


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