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)

Two highly lead-sensitive ATPases, Na+,K+-ATPase and adenylate cyclase, can be demonstrated cytochemically by the lead precipitation technique in briefly prefixed tissue, provided that the free Pb2+ concentration in the incubation medium is kept below 0.1 mM by a heavy metal chelator. Under conditions suitable for Na+,K+-ATPase activity precipitation of final reaction product (lead phosphate) at the sarcolemma of cardiac muscle is abolished by 0.1-1mM ouabain. In contrast, reaction product deposition at the intramuscular part of the plasma membrane and at intracellular sites is not noticeably affected by the glycoside. These findings indicate either that the sarcolemma is the exclusive location of Na+,K+-ATPase in cardiac muscle or that the presence of the enzyme at other loci is masked by active Na+,K+-independent, ouabain resistant ATPases. Under conditions favoring adenylate cyclase activity, precipitation by Pb2+ of orthophosphate derived, with the help of added cyclic nucleotide phosphodiesterase and 5'-nucleotidase, from cyclic AMP formed from adenylyl imidodiphosphate (AMP-PNP) is seen after prolonged incubation in myocardial cells along the entire course of the plasma membrane and also at the transverse tubules and is particularly intense at the tight junction regions of the intercalated disks. Ouabain has no effect on these reactions. Reaction product deposition is also observed at the sarcolemma in red skeletal muscle and at the terminal cisternae of the sarcoplasmic reticulum in white skeletal muscle, where the reaction is intensified by adrenaline. Sarcoplasmic reticulum of cardiac and of red skeletal muscle exhibits only relatively weak staining attributable to cyclic AMP formation. These observations are in agreement with the results of tissue fractionation studies according to which the plasma membrane is the chief site of adenylate cyclase in heart and in red, but not white skeletal muscle.
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PMID:Cytochemical studies on sarcolemma: Na+, K+-adenosine triphosphatase and adenylate cyclase. 13 Jun 56

Sarcolemmal Ca++-ATPase, Mg++-ATPase, and (Na+-K+)-ATPase activities were increased in late stages of heart failure in myopathic hamsters (BIO 14.6) without any changes in the adenylate cyclase activity. On the other hand, these hamsters at early and moderate stages of heart failure showed depressions in mitochondrial calcium binding and uptake and microsomal calcium binding. Sarcolemmal (Na+-K+)-ATPase was decreased in failing hearts because of substrate lack, oxygen lack, and perfusion with Ca++-free, Na+-free, or K+-free medium. Both Mg++-ATPase and Ca++-ATPase activities of sarcolemma did not change on perfusing the hearts with substrate-free, hypoxic, Na+-free, or K+-free medium. Adenylate cyclase activity decreased on substrate-free or Ca++-free perfusion. Intracellular calcium overload produced by perfusing the hearts with medium containing calcium after Ca++-free perfusion was associated with decrease in all the sarcolemmal-bound enzyme activities. All types of failing hearts employed in this study showed a dramatic shift in the electrolyte composition. Failure of the cardiac muscle to generate contractile force on treatment with trypsin was associated with defects in the functions of sarcolemma, mitochondria, and sarcoplasmic reticulum, whereas such an effect on treatment with phospholipase C was limited to alterations in the activities of sarcolemma. The data suggest that abnormality at the level of sarcolemma plays an important role in the pathogenesis of heart dysfunction; however, the degree and direction of alterations in the sarcolemmal functions seem to be dependent upon the type of heart failure.
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PMID:Role of sarcolemmal changes in cardiac pathophysiology. 13 Jun 63

Based upon literature and our own experimentation on Goldblatt rats, the significance of a decrease of the maximal shortening velocity of the myocardium at zero load (Vmax) in the hypertrophied, chronically pressure-loaded heart is discussed. In the hypertrophied myocardium with varying concentrations of the contractile structures, the developed tension under isometric conditions (sigma) and the maximum rate of tension development (d sigma/dtmax) can indicate significant deviations from the values of controls of the same age, without, however, making it possible to draw from these changes absolute conclusions about the elementary contractile process. With the enhanced concentration of contractile proteins, the mentioned isometric values, as well as the maximum instantaneous power (cross-sectionally related) of the myocardium can be increased during a stage of hypertrophy in which Vmax is already reduced. The decrease of Vmax shows a rough correlation with the reduction of the specific ATPase activity of actomyosin and is already observed at moderate degrees of hypertrophy (30 to 50%). The time course of the change of both parameters in experimental hypertrophy suggests a causal relation between the changes of those two parameters and the failure of the myocardium in later stages of a chronic overload. Under the condition of reliable estimation, Vmax allows for, also with changed actomyosin concentration, an assessment of the elementary contractile process. On the other hand, Vmax does not present a sufficient measure for the cross-sectionally related power capacity of the hypertrophied myocardium. The possible dissociation between the unloaded shortening velocity and the cross-sectionally related power capacity could, in certain cases, explain an unsatisfactory correlation between Vmax and the clinical state of the heart. The so-called empirical indices of contractility, which are not always clearly related to basic physiological characteristics of the myocardium, should be interpreted with particular reserve in relation to the hypertrophied cardiac muscle.
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PMID:[Maximum velocity of load-free shortening Vmax, myocardial capacity and "contractility indices" in the hypertrophic myocardium]. 13 30

A method is described for the purification of troponin from beef skeletal muscle. The resultant preparation differs from the troponin of rabbit skeletal muscle in that it contains at least two forms of the tropomyosin-binding component, Troponin-T: these are designated as the 37 000 and 40 000 dalton forms of Troponin-T on the basis of sodium dodecyl sulphate gel electrophoresis. Either of these Troponin-T forms may be used to reconstitute troponin by mixing with the appropriate amounts of the calcium-binding (Troponin-C) and and actomyosin ATPase-inhibitory (Troponin-I) components. These reconstituted troponins are shown to interact with tropomyosin and also to confer full calcium sensitivity on actomyosin ATPase. Despite the existence of proteolysis in troponin preparations, the experimental evidence indicates that the smaller form of Troponin-T is not derived from the 40 000 dalton species by limited degradation. Although both species of Troponin-T have been found routinely in troponin from beef skeletal muscle, only the larger form is detected in troponin preparations from beef cardiac muscle. Further studies are required in order to clarify the functional significance and differential distribution of these multiple forms of Troponin-T.
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PMID:Beef muscle troponin: evidence for multiple forms of troponin-T. 13 78

A study of myosin extracted from dog's cardiac muscle at different stages of chronic heart failure (from 1 week to 1 year) was carried out. A decrease of UV-luminescence intensity, flow birefringence and ATPase activity (to 70%) was observed. The electron microscopic investigation of myosin and LMM structure shows the loss of ability to form typical paracrystals by LMM, the electron microscopic appearance of the whole myosin being unchanged.
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PMID:[Structural and functional changes in myosin in chronic coronary insufficiency]. 13 86

The contractile properties and contractile protein enzymatic activity of skeletal muscle can be altered by neural influences. To determine whether similar influences apply to cardiac muscle, adult rats were chemically sympathectomized by intravenous injection of 6-hydroxydopamine (6-OHDA). After 2 weeks of treatment, rats were anesthetized and an index of myocardial contractility (max dP/dt) was measured in situ. Max dP/dt was depressed in 6-OHDA-treated rats [4560 +/- 420 (mean +/- SE) mm Hg/sec] when compared to controls (6710 +/- 580 mm Hg/sec). Sympathectomy was verified by reduced hemodynamic responsiveness to tyramine injections. After functional measurements had been completed, the heart was excised. Myofibrils were prepared from left ventricular tissue and analyzed for ATPase activity. Myofibrillar protein yield averaged 38 +/- 2 mg/g in controls and was not significantly different in 6-OHDA rats. Myofibrillar ATPase activity was 0.314 +/- 0.014 mumol P1/mg per min in controls. Enzyme activity was significantly reduced to 0.230 +/- 0.020 mumol P1/mg per min in 6-OHDA rats. The results demonstrate that a chronic reduction in sympathetic stimulation to the heart results in a depression of an index of myocardial contractile function which is accompanied by reduced myofibrillar ATPase activity. Acute (16-18 hours) chemical sympathectomy depressed the contractile function index without altering ATPase activity. Bilateral adrenalectomy produced no further decrement in myofibrillar ATPase activity in chronically (2 weeks) sympathectomized rats. Therefore, it appears that the changes in contractile protein enzymatic properties are mediated by sympathetic neural influences and may involve the synthesis of new contractile protein(s) with altered enzymatic properties.
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PMID:Myocardial contractile function and myofibrillar adenosine triphosphatase activity in chemically sympathectomized rats. 13 56

The calcium activation of the ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity of cardiac actomyosin reconstituted from bovine cardiac myosin and a complex of actin-tropomyosin-troponin extracted from bovine cardiac muscle at 37 degrees C was studied and compared with similar proteins from rabbit fast skeletal muscle. The proteins of the actin complex were identified by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Half-maximal activation of the cardiac actomyosin was seen at a calcium concentration of 1.2 +/- 0.002 (S.E. of mean) muM. A hybridized reconstituted actomyosin made with cardiac myosin and the actin-tropomyosin-troponin complex extracted from rabbit skeletal muscle was also activated by calcium but the half-maximal value was shifted to 0.65 +/- 0.02 (S.E. of mean) muM Ca2+. Homologous rabbit skeletal actomyosin showed half-maximal activation at 0.90 +/- 0.01 (S.E. of mean) muM Ca2+ and the value for a hybridized actomyosin made with rabbit skeletal myosin and the actin-complex from cardiac muscle was found at 1.4 +/- 0.03 (S.E. of mean) muM Ca2+ concentration. Kinetic analysis of the Ca2+ activated ATPase activity of reconstituted bovine cardiac actomyosin indicated some degree of cooperativity with respect to calcium. Double reciprocal plots of reconstituted actomyosins made with bovine cardiac actin complex were curvilinear and significantly different than those of reconstituted actomyosins made with the rabbit fast skeletal actin complex. The Ca2+-dependent cooperativity was of a mixed type as determined from Hill plots for homologous reconstituted bovine cardiac and rabbit fast skeletal actomyosin. The results show that cooperative interactions in reconstituted actomyosins were greater when the actin-tropomyosin-troponin complex was derived from cardiac than skeletal muscle.
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PMID:Cooperative interactions between the contractile proteins of cardiac and skeletal muscle. 13 46

The effects of chronic "steady-state" and high-speed interval running were investigated on time-course changes in certain biochemical properties of cardiac and skeletal muscle fiber types of rats. Nine weeks of the interval program resulted in significant increased (15%) in both cardiac enlargement and ATPase activity of myofibrils; whereas increases in these parameters were only transient and not significant at the termination of the program involving steady-state running. Neither program induced appreciable alterations in citrate synthase and phosphofructokinase activity in cardiac muscle. In fast-twitch white fibers, "steady-state" training induced only a transient 45% increase in citrate synthase activity in contrast to a progressive twofold change with interval training. Both programs resulted in similar increases (45-50%) in citrate synthase activity in fast-twitch and slow-twitch red fibers. However, the patterns of increase for both fiber types differed between the two programs. These findings suggest that training programs incorporating elements of both "steady-state" incline and high-speed interval running can potentially induce respiratory enzyme adaptations in the greatest spectrum of rodent skeletal muscle fibers in addition to inducing adaptations to enhance contractile potential in cardiac muscle.
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PMID:Time course adaptations in cardiac and skeletal muscle to different running programs. 13 67

The main parameters of contraction and relaxation of papillary muscle strips taken from the left ventricle of control and exercise-adapted rats were measured. The contractile velocity and amplitude of thin and thick strips of the cardiac muscle of adapted rats were found to be 2--3 times higher than in the controls. This fact can be explained by an elevation of myosine ATP-ase activity. The developed tension was higher than in the controls only in thick strips of adapted rats. This increase depends on the adaptive augmentation of the functional power of systems responsible for the transport of oxygen and substrates to the mitochondria. The myocardium of adapted rats differed from that of the controls in that the relaxation velocity and compliance were significantly elevated. These facts suggested an increase in the funcitonal power of the ionic transport system that is responsible for Ca++ elimination from the myofibrils. In general, the results suggest that an elevation of maximal myocardial performance after adaptation to exercises may be due to a coordinative increase in the power of three basic systems of the myocardial cells--ion transport system, myosine ATPase and resynthesis ATP system.
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PMID:[Mechanism of increasing the functional capacity of the cardiac muscle after adaptation to physical exertion]. 13 93

Fifty-seven isolated, blood perfused, continuously weighed canine hearts have been utilized to study the development of abnormal myocardial fluid retention during early myocardial ischemic injury. Inflatable balloon catheters were positioned around the left anterior descending coronary arteries (LAD) of 54 hearts or the proximal left circumflex coronary arteries of three hearts for study of the following intervals of coronary occlusion: a) 10 minutes followed by 20 minutes of reflow, b) 40 minutes followed by either no reflow or by 20 minutes of reflow, and c) 60 minutes without reflow. After 60 minutes of fixed coronary occlusion, histologic and ultrastructural examination revealed mild swelling of many ischemic cardiac muscle cells in the absence of interstitial edema, cardiac weight gain, and obvious structural defects in cell membrane integrity. After 40 minutes of coronary occlusion and 20 minutes of reflow, significant cardiac weight gain occurred in association with characteristic alterations in the ischemic region, including widespread interstitial edema and focal vascular congestion and hemorrhage and swelling of cardiac muscle cells. Focal structural defects in cell membrane integrity were also noted. The development of abnormal myocardial fluid retention after 40 minutes of LAD occlusion occurred in association with a significant reduction in sodium-potassium-ATPase activity in the ischemic area, but with no significant alteration in either creatine phosphokinase or citrate synthase activity in the same region. Despite the abnormal myocardial fluid retention in these hearts, it was possible pharmacologically to vasodilate coronary vessels with adenosine and nitroglycerin infusion to maintain a consistently high coronary flow following release of the coronary occlusion after 40 minutes and to even exceed initial hyperemic flow values following release of the occlusion when adenosine and nitroglycerin infusion was delayed until 15 minutes after reflow. Thus, the data indicate that impaired cell volume regulation and interstitial fluid accumulation and focal structural defects in cell membrane integrity are early manifestations of ischemic injury followed by reflow, but fail to establish a major role for the abnormal fluid retention in altering coronary blood flow prior to the development of extensive myocardial necrosis. In contrast, fixed coronary occlusion for 60 minutes results in mild intracellular swelling but no significant interstitial edema and no obvious structural defects in cell membrane integrity.
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PMID:Abnormal myocardial fluid retention as an early manifestation of ischemic injury. 13 29


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