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)

Canine kidneys were preserved under hypothermia in Collins' standard solution and the contents of sodium, potassium, and Na+ and K+-ATPase in several parts of these kidneys were followed. Hypothermic preservation in combination with single perfusion by means of Collins' solution without thermic ischemia caused loss of sodium, increase of potassium, and decrease of the total osmotic cortico-papillary gradient of the kidney. No loss of Na+ and K+-ATPase activity occurred under these conditions. The determination of Na+ and K+-ATPase level in the renal tissue turns out to be a rational method to assess the vitality of an organ to be transplanted.
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PMID:[Effect of Collins' solution the kidney concentrating gradient and the Na+ and K+-ATPase of the kidney]. 21 72

The energy production (heat + work) of cardiac muscle must be interpreted in terms of the major ATPases underwriting cardiac contraction; these are the Ca2+ and Na+-K+ transport ATPases and actomyosin ATPase. It is possible to apply the classical phenomenological subdivisions to cardiac energy production; when this is done, certain properties immediately distinguish cardiac muscle from skeletal muscle. Little or no temporal distinction exists between initial (anaerobic) and recovery (oxidative) metabolism. Even at temperatures as low as 20 degrees C most of the recovery heat is released within the time course of a single contraction. Cardiac muscle is characterized by a high resting heat rate, the magnitude of which varies between species and depends on the metabolic substrate. In isometric contractions there is a slightly curvilinear relationship between developed force and heat production. There is a tension-independent or activation component, the magnitude of which reflects the prevailing level of contractility and is probably associated with calcium release and retrieval. In isotonic contractions energy production is maximal when the muscle is heavily loaded but falls steeply when the size of the load is reduced. The enthalpy:load relation is probably similar to that found in twitch contractions of skeletal muscle working at room temperature or above; but, unlike for skeletal muscle, there are families of such curves: At any instant of time the relation depends upon the prevailing physiological conditions (e.g. stimulus rate, substrate supply, humoral agents, extracellular ionic concentrations, initial length). Cardiac energy production can be estimated by a variety of other techniques (such as high-energy phosphate utilization, oxygen consumption, and changes in tissue fluorescence related to pyridine nucleotide oxidation levels). At the present time there is considerable agreement between heat measurements and results obtained with these different techniques. We should like to conclude on a cautionary note. First, there is considerable variability in the properties of cardiac muscle from different species. Significant variations occur at nearly all levels of cellular function--e.g. shape of action potential, electrical and mechanical dependence upon stimulus history, mechanisms of excitation-contraction coupling, actomyosin ATPase activity, metabolic regulation, and differential sensitivity to anoxia or ischemia. Second, the types of contractions readily studied in isolated papillary muscles (i.e. isometric or isotonic twitches) may not necessarily be the best mechanical paradigms for understanding myocardial energetics in vivo. The particular geometric demands of individual research techniques require the use of a wide variety of myocardial preparations from a wide variety of species. This necessarily produces a pastiche view of cardiac muscle rather than an integrated picture of some hypothetically typical mammalian myocardium.
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PMID:Cardiac heat production. 21 64

Intravenous infusion of acetylstrophanthidin to 6 dogs, after a 60 min left anterior descending coronary artery occlusion, was associated with a 43.0 +/- 10.5% decrease in the dose of digitalis needed to produce ventricular arrhythmias as compared to the pre-ischemic dose (97.5 +/- 8.0 microgram/kg). Reperfusion of the ischemic region for 2 h after a 90 min occlusion resulted in a 54.4 +/- 6.7% decrease in the arrhythmogenic dose. Direct intracoronary infusions of digitalis into the ischemic region, after a 90 min coronary occlusion followed by 2 h of reperfusion, was associated with a 47.7 +/- 6.4% decrease in the dose of digitalis needed to produce arrhythmias. The pre-ischemic (control) arrhythmogenic dose of digitalis via the intracoronary infusion method was 1.5 +/- 0.3 microgram/kg (mean +/- S.E.M. of 7 dogs). Sodium pump activity, estimated from the ouabain-sensitive 86Rb uptake in sodium-loaded ventricular slices, was significantly higher in slices obtained from the ischemic regions (6.84 +/- 0.30 nmoles 86Rb/mg dry wt. (mean +/- S.E.M.), than from the non-ischemic regions (3.43 +/- 0.64 nmoles 86Rb/mg dry wt.). Sensitivity of the sodium pump activity to the inhibitory effect of ouabain also was increased in the ischemic regions as indicated by a shift in the log dose--response curve to the left. Thus, it appears that there is an increase in myocardial sensitivity to the toxic effect of digitalis after temporary ischemia and it appears to be related to an increase in the sensitivity of the Na+,K+-ATPase or sodium pump to the inhibitory effect of digitalis.
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PMID:Ischemic-induced alterations in cardiac sensitivity to digitalis. 48 58

1. Changes of structural proteins in experimental and human myocardial infarction were studied by the determination of myosin- and actomyosin-ATPase activities and gel electrophoretic analysis in the presence of sodium dodecyl sulfate (SDS). 2. In animal experiments using dogs, the relative amounts of myosin and alpha-actinin decreased at 24 to 48 hours after coronary ligation, became lowest at 72 hours, and remained at this level for 2 weeks and returned to almost normal value at 28 days. 3. Myosin- and actomyosin-ATPase activities decreased rapidly during 24 to 48 hours after ligation with temporary increase in their activities in the initial stage of ischemia and followed the similar time course as that of the amounts of myosin and alpha-actinin. 4. SDS gel electrophoretic analysis of structural proteins of infarcted tissues of the human hearts obtained from 5 cadavers showed also marked decrease of the contents of myosin and alpha-actinin with relative preservation of actin, tropomyosin and troponin-T.
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PMID:Changes of cardiac structural proteins in myocardial infarction. 92 15

Mitochondrial respiration, succinate dehydrogenase coenzyme Q reductase, and myosin B were investigated in ischemic myocardium from experimental myocardial infarction in dogs. Respiratory control ratio of mitochondria was impaired by ischemia at 60 min after coronary ligation, and oxygen consumption was inhibited 120 min later. Enzyme activity of succinate dehydrogenase coenzyme Q reductase was decreased at 6 hr after coronary ligation. Calcium ion sensitivity of myosin B declined 12 hr after coronary ligation. However, adenosine triphosphatase activity of myosin A from infarcted myocardium was not different from that of the intact one. These results suggest that interaction in the sequence of enzyme complexes was first impaired in ischemic myocardium and that deterioration of enzyme activity was then manifested.
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PMID:Relationship between energy liberation and utilization in ischemic cardiac muscle. 103 51

Histologic investigations together with histochemical and photometric measurements of enzyme activities were performed in retina of rabbits, whose blood supply had been totally interrupted for 1h. A retinal edema developed affecting the internal layers between the inner limiting membrane and the internal plexiform and ganglion cell layer. Although this edema was quite remarkable at the posterior pole of the eye, it diminished toward the periphery, disappearing near the ora serrata. The activities of the following enzymes were investigated: hexokinase, glucose 6-phosphate dehydrogenase, aldolase, glyceraldehydephosphate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, ATPase, and phosphorylase. The most striking finding was the total disappearance of phosphorylase activity under pressure ischemia. ATPase and aldolase showed a decreased activity in the ischemic retina, and malate dehydrogenase a slightly diminished one. Concerning the other enzymes, no significant differences between normal and ischemic retina were observed.
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PMID:Enzymologic and histologic investigations in normal and pressure-ischemic retina of rabbits. 108 79

The permissible duration of brain ischemia without sustaining damage is short. Less clear are the mechanisms accounting for the vulnerability of brain to ischemic insults. Neurochemical factors implicated include impairment of energy synthesis by mitochondria and of energy-dependent processes such as synaptic transmission, ATPase activity, membrane conductance and altered protein and lipid synthesis. To clarify the vulnerability of energy metabolism, we investigated energy availability and synthesis in our model of global cerebral ischemia. Our studies evaluated in vitro mitochondrial ATP synthesis and the in vivo quantitation of the cortical adenylate pool. Results of our investigations support a growing body of evidence showing the energy state to be relatively stable to ischemia. We conclude that an energy-dependent process of brain is primarily vulnerable to ischemia.
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PMID:Energy metabolism during brain ischemia. Stability during reversible and irreversible damage. 119 33

The effect of coronary reperfusion on the uptake of cardiac glycosides by ischemic myocardium was studied in 17 open chested dogs undergoing anterior wall infarction produced by snaring confluent branches of the left coronary system. Epicardial electrograms delineated ischemic zones of S-T elevation, border, and nonischemic zones. Animals were reperfused by snare release 1, 2, and 6 hr after occlusion. After 15 min of reperfusion, 1.0 mg of [3H] digoxin was given intravenously, and 2 hr later the hearts were excised and endocardial (endo) and epicardial (epi) samples from each zone were analyzed for [3H] digoxin concentration. In five dogs occluded for 1 hr and reperfused, [3H] digoxin uptake was comparable in endo and epi layers of all three zones. In six dogs reperfused after 2 hr of occlusion, mean (+/-S.E.) [3H] digoxin concentrations (nanograms per gm) were significantly reduced by 54 percent in endo (111 +/-18) and 35 percent in epi (151 +/- 23) layers of the ischemic zone as compared with the mean nonischemic concentration (endo249 +/- 34; epi 239 +/- 34). Border zone endo and epi [3H] digoxin uptake was reduced by 21 and 17 percent, respectively. In six dogs reperfused after 6 hr of occlusion, [3H] digoxin uptake in the ischemic zone was markedly reduced by 85 percent in endo (34 +/- 4) and 60 percent in epi (86 +/- 12) layers as compared with the nonischemic concentration (endo 232 +/- 19; epi 217 +/- 15). Border zone uptake was decreased by 54 percent in endo and 38 percent in epi regions. We conclude that coronary reperfusion between 2 and 6 hr of coronary occlusion is associated with markedly reduced myocardial digoxin uptake, more pronounced in subendocardial regions of ischemic tissue. This alteration in digoxin binding by reperfused ischemic myocardium is consistent with ischemia-induced structural or functional alterations in the putative digitalis receptor, (Na++K+)-ATPase.
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PMID:Effects of ischemia and reperfusion on myocardial uptake of tritiated digoxin. 125 85

Myocardial hypertrophy in response to elevated myocardial wall stress largely results from myocyte hypertrophy. In congestive heart failure, this hypertrophy can have compensatory as well as critical relevance. On the one hand, it reduces myocardial wall stress in the case of hemodynamic overload by enhancing ventricular wall thickness. On the other hand, risks and problems may result from the tissue changes associated with myocardial "overload-hypertrophy", such as alterations in myocyte phenotype, augmentation of connective tissue in the myocardium, reductions in coronary reserve (even without altherosclerotic coronary stenoses), and alterations in the local formation of growth cofactors (i.e., enhanced myocardial expression of angiotensinogen and converting enzyme). Changes in myocyte phenotype occur in receptor signal transduction, in isoform shifts of contractile proteins and of key enzymes in energy metabolism towards a more fetal-like pattern, and in a "fragility" of Ca(++)-homeostasis (due to reduced expression of sarcoplasmic reticulum Ca(++)-ATPase and enhanced expression of membrane Na+/Ca(++)-exchange in presence of maintained density of Ca(++)-channels). Additionally, the fraction of contractile fibers and mitochondria per myocyte cross-section can be reduced with attenuated systolic function. The fragility of Ca(++)-homeostasis must be regarded as potentially critical because of retarded inactivation of contraction and because of susceptibility to diastolic Ca(++)-overload with delayed after-depolarizations. Additionally, diastolic dysfunction may result from interstitial fibrosis and ischemia due to reduced coronary reserve (altered vascular structure and endothelial dysfunction).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[The significance of myocardial hypertrophy in heart failure]. 129 Mar 5

Using Langendorff's perfusion model of isolated rat heart, the effect of period of ischemia, ischemia-reperfusion and changes in perfusate pH on the function of calcium uptake of cardiac sarcoplasmic reticulum (SR) was observed. The initial rate and capacity of calcium uptake by SR decreased significantly after 25 min ischemia, and were further worsened when ischemia was prolonged to 40 min. When hearts were subjected to 15 min reperfusion after 25 min ischemia, calcium uptake capacity and initial rate decreased even more in comparison with that of 40 min ischemia. In addition, the calcium dependent ATPase activity of SR was also markedly inhibited. Reperfusion with acid (pH 6.8) or alkaline (pH 8.0) made no significant difference on the aforementioned reperfusion induced changes. The results indicated that myocardial ischemia depressed the calcium transport activity of SR, and this depression was further aggravated with prolonging ischemia. Reperfusion after ischemia exacerbated the ischemic injury. Reperfusion with either acid or alkaline Krebs-Henseleit solution could not improve the calcium uptake function of SR, implying that the pH change does not seem to be an important factor in inducing the SR dysfunction during ischemia-reperfusion.
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PMID:[Alteration of calcium uptake and Ca(2+)-ATPase activity of cardiac sarcoplasmic reticulum in rat during ischemia-reperfusion]. 129 51


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