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)

The present study evaluates 3H-ouabain binding site (Na,K-ATPase) concentration in left ventricular myocardium of dogs with heart failure induced by tachycardia as a result of ventricular pacing. Samples of left ventricle were obtained from 10 dogs exposed to pacing of 240 beats/min for 3 to 4 weeks and eight sham-operated controls. Na,K-ATPase was quantified using vanadate facilitated 3H-ouabain binding to intact samples. At time of sacrifice paced dogs showed clinical signs of heart failure, a significant 257% increase in left ventricular end diastolic pressure and a significant 46% decrease in left ventricular dP/dt compared with control. There was no significant change in left ventricular mass. 3H-ouabain binding concentration was significantly reduced by 16%. Evaluation of 3H-ouabain binding kinetics revealed no significant difference between myocardium from paced and control dogs: Equilibrium binding conditions were at the various concentrations used obtained after similar incubation time; nonspecific uptake and retention of 3H-ouabain was 0.9-0.8% of total uptake and retention obtained in the standard assay; apparent dissociation constant (KD) was 6.5 x 10(-8)-6.6 x 10(-8) mol/l; loss of specifically bound 3H-ouabain during washout at 0 degrees C occurred with a half-life time (T1/2) of 120 and 121 h. Hence, total 3H-ouabain binding site concentration in left ventricular myocardium was (mean +/- SEM) 1110 +/- 56 and 1317 +/- 68 pmol/g wet weight, 8.54 +/- 0.43 and 10.05 +/- 0.52 pmol/mg protein, and the total amount of 3H-ouabain binding sites in the entire left ventricle 121 +/- 6 and 162 +/- 8 nmol in paced (n = 10) and control (n = 8) dogs (p < 0.05), respectively. In conclusion, the present study reports a significant reduction in left ventricular myocardium 3H-ouabain binding site concentration in tachycardia induced heart failure. This observation supports the concept of a relationship between Na,K-ATPase concentration and contractile capacity and may be of pathophysiological importance in tachycardia and heart failure.
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PMID:Reduced 3H-ouabain binding site (Na,K-ATPase) concentration in ventricular myocardium of dogs with tachycardia induced heart failure. 814 25

Cytosolic free sodium concentration ([Na+]i) and sodium transport systems were measured in intact platelets from 19 patients with early-stage chronic renal failure and 33 healthy control subjects using the novel fluorescent dye sodium-binding-benzofuran-isophthalate. Resting [Na+]i was significantly greater in patients with chronic renal failure compared to control subjects (40.8 +/- 3.1 mmol/l versus 32.2 +/- 2.0 mmol/l, mean +/- SEM, P < 0.05). After inhibition of Na-K-ATPase by 1 mmol/l ouabain a higher net sodium influx was observed in platelets from patients with chronic renal failure compared to control subjects (49.8 +/- 8.7 mmol/l versus 28.5 +/- 5.2 mmol/l, P < 0.05). The platelet Na-H exchanger was similar in the two groups. Cytosolic free calcium concentration ([Ca2+]i) was measured using fura2 and did not show significant differences between the two groups. To evaluate whether a circulating factor may be associated with elevated [Na+]i, a linked-enzyme Na-K-ATPase assay was included. Compared to control subjects plasma from patients with chronic renal failure produced a significant inhibition of steady-state Na-K-ATPase activity by 11.2 +/- 3.0% (P < 0.01). It is concluded that early-stage renal failure is associated with significant impairment of platelet sodium metabolism.
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PMID:Increased cytosolic free sodium in platelets from patients with early-stage chronic renal failure. 817 73

Resting heat rate was measured in superfused rabbit papillary muscles at 20 degrees C during 40 minutes of anoxia and subsequent reoxygenation. To reveal the nature of the reactions underlying energy output under such conditions, the data obtained were compared with values predicted from data on chemical change. Before and after the anoxic period, muscles were stimulated at 0.2 Hz, during which time the contraction-related heat rate was measured. During anoxia, muscles were kept at rest or stimulated at 1 Hz. Stimulation was switched off intermittently to determine resting heat rate. Before anoxia, resting heat rate was 8.7 +/- 1.1 (mean +/- SEM) mW.g dry wt-1. During anoxia, it decreased to 38% and 50% of the preanoxic level in resting and stimulated muscles, respectively (P < .05). In resting muscles, heat rate increased with reoxygenation in approximately 10 to 15 minutes to 1.3 times the preanoxic level, whereas this was 3.7 times in stimulated muscles. Resting heat rate returned within 65 (resting muscles) or 150 (stimulated muscles) minutes to the baseline. The ratio of force- and contraction-related heat rate, ie, the economy of contraction, was not different before and after anoxia. We estimated that the heat produced by muscles during anoxia was not different from the heat to be expected from the hydrolysis of creatine phosphate, the breakdown of nucleotides, and the formation of lactate. The overshoot in resting heat during reoxygenation of resting muscles could be accounted for by the resynthesis of the energy store. The much larger overshoot in resting heat of stimulated muscles was due to the contracture. The finding that the economy of contraction was not altered by anoxia and reoxygenation suggests that both sarcoplasmic reticulum Ca(2+)-ATPase and myofibrillar ATPase are depressed by anoxia and that the enhancement of cytosolic calcium transients with reoxygenation, reported in other studies on papillary muscle, results from reduced binding of calcium rather than from enhanced release.
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PMID:Heat produced by rabbit papillary muscle during anoxia and reoxygenation. 822 88

The HGT-1 human gastric cell line is similar to acid secreting parietal cells in that it possesses H2 receptors, histamine sensitive adenyl cyclase, and Cl- channels, which are activated by histamine by a cyclic adenosine monophosphate (cAMP) dependent mechanism. To discover if HGT-1 cells have additional properties found in parietal cells, [3H]omeprazole and patch clamp recording techniques were used to evaluate specific omeprazole binding sites and K+ channels in the plasma membrane. HGT-1 cells exhibited [3H]omeprazole binding in the non-stimulated state, which increased 100% in the presence of 1 mM histamine. High conductance (about 155 pS) K+ channels were active spontaneously in 17% of cell attached or excised inside out patches in non-stimulated subconfluent HGT-1 cells. In inside out patches, channel activity increased fivefold during depolarisation, ion substitution experiments confirmed that the channels were highly selective for K+, and channel activity was almost abolished by removal of Ca2+ or addition of 5 mM Ba2+. In quiescent cell attached patches, 0.1 mM dibutyryl cAMP failed to activate K+ channels. In contrast, 6.7 microM A23187 (a Ca2+ ionophore) increased intracellular Ca2+ concentration from mean (SEM) 14 (3) nM to 248 (30) nM and activated K+ channels in 21% of patches. It is concluded that the plasma membrane of HGT-1 cells possesses (a) specific 3H-omeprazole binding sites, which may reflect the omeprazole sensitive H+,K(+)-ATPase present in gastric parietal cells; and (b) Ca(2+)-activated K+ channels, which may be located in the basolateral membrane of human gastric parietal cells and play a part in acid secretion triggered by Ca(2+)-mediated secretory agonists.
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PMID:Properties of a potassium channel in cultured human gastric cells (HGT-1) possessing specific omeprazole binding sites. 824 97

Membrane potential of rabbit corneal endothelial cells measured using microelectrodes was -29.3 +/- 0.8 mV, n = 45, (mean +/- SEM). Histological location of Lucifer Yellow dye iontophoresed out of the microelectrode confirmed that the microelectrode was located intracellularly. The Lucifer Yellow diffused five to six cell diameters away from the impaled cell indicating endothelial cell coupling. Depolarization by ouabain (10(-4) M) and high extracellular potassium (potassium for sodium substitution) showed the cells to be responsive to changes in the bathing solution whilst impaled, that the cell membrane is more permeable to potassium than sodium and that membrane bound Na(+)-K(+)-ATPase activity generates the transmembrane electrolyte gradients.
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PMID:Rabbit corneal endothelial cell membrane potential. 826 74

The transgenic rat TGR(mRen2)27 is a new monogenetic model in hypertension research that develops fulminant hypertension after the mouse Ren-2d renin gene has been integrated into its genome. To evaluate the molecular mechanism of development of hypertension in this animal model, we measured cytosolic free sodium concentration in intact lymphocytes from seven transgenic rats and eight age-matched normotensive Sprague-Dawley rats using the novel sodium-sensitive fluorescent dye sodium-binding benzofuranisophthalate. Resting cytosolic sodium was significantly higher in transgenic rats compared with Sprague-Dawley rats (31.7 +/- 2.2 versus 18.2 +/- 0.4 mmol/L, mean +/- SEM, P < .001). Inhibition of Na,K-ATPase by 0.5 mmol/L ouabain for 5 minutes significantly increased lymphocytic cytosolic sodium in Sprague-Dawley rats to 36.5 +/- 3.4 mmol/L (P < .001 compared with resting value), whereas no significant change could be observed in transgenic rats (35.4 +/- 0.6 mmol/L), indicating that Na,K-ATPase is less responsive in transgenic rats. The Na,K-ATPase activity from erythrocytes was measured with an enzyme-linked assay. Na,K-ATPase activity was significantly reduced in transgenic rats compared with Sprague-Dawley rats (4.0 +/- 0.3 versus 8.1 +/- 0.6 U/L, P < .001). We concluded that reduced Na,K-ATPase activity leads to elevated cytosolic sodium in this model of genetic hypertension.
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PMID:Increased cytosolic sodium and reduced Na,K-ATPase activity in transgenic rats. 828 58

Speculations about development of tolerance to the inotropic effect of digitalis have been engendered since studies in various in vitro systems and tissues not representative of the heart have shown up-regulation of sodium potassium adenosine triphosphatase (Na,K-ATPase) when exposed to digitalis. Moreover the digitalis receptor (i.e., Na,K-ATPase) concentration in the normal, vital human left ventricle has not been previously determined. On this basis, digitalis receptor concentration was quantified in the left ventricle of explanted hearts from subjects without heart disease and from patients with end-stage heart failure who had received digitalis therapy. This was performed using vanadate-facilitated 3H-ouabain binding to intact tissue samples giving values of 728 +/- 58 (n = 5) and 467 +/- 55 pmol/g wet weight (n = 6) (mean +/- SEM) (p < 0.005), respectively. However, some of the digitalis receptors may have retained digoxin before 3H-ouabain binding and thus may have escaped detection. To eliminate this effect of retained digoxin, samples were exposed to prolonged washing in buffer containing excess digoxin antibody, a method recently shown to clear digoxin from receptors and allow subsequent complete digitalis receptor quantification by 3H-ouabain binding. After washing in digoxin specific antibody, specific digitalis receptor concentration was 760 +/- 58 pmol/g (n = 5) and 614 +/- 47 pmol/g (n = 6) wet weight in samples of the normal and failing hearts, respectively (p < 0.08). Thus, digitalization was associated with occupancy of digitalis receptors in the failing human heart of 24% (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:No adaptation to digitalization as evaluated by digitalis receptor (Na,K-ATPase) quantification in explanted hearts from donors without heart disease and from digitalized recipients with end-stage heart failure. 838 May 32

The aims of the present study were to evaluate in humans the putative importance of skeletal muscle digitalis glycoside receptors (Na,K-ATPase) in the volume of distribution of digoxin and to assess whether therapeutic digoxin exposure might cause digitalis receptor upregulation in skeletal muscle. Samples of the vastus lateralis were obtained postmortem from 11 long-term (9 months to 9 years) digitalized (125-187.5 micrograms daily) and eight undigitalized subjects. In intact samples from digitalized patients, vanadate-facilitated 3H-ouabain binding increased 15% (p < 0.02) from 150 +/- 18 to 173 +/- 13 pmol/g wet wt. (mean +/- SEM) after clearing receptors of bound digoxin by washing samples in excess specific digoxin antibody fragments. 3H-ouabain binding in the untreated group was 257 +/- 28 and 274 +/- 26 pmol/g wet wt. (7%, p > 0.30) before and after washing in specific digoxin antibody fragments, respectively. Thus, the present study indicates a approximately 13% occupancy of skeletal muscle digitalis glycoside receptors with digoxin during digitalization. In light of the large skeletal muscle contribution to body mass, this indicates that the skeletal muscle Na,K-ATPase pool constitutes a major volume of distribution for digoxin during digitalization. The results gave no indication of skeletal muscle digitalis glycoside receptor upregulation in response to digoxin treatment. On the contrary, there was evidence of significantly lower (37%, p < 0.005) digitalis glycoside receptor concentration in the vastus lateralis of the digitalized patients, which may be of importance for skeletal muscle incapacity in heart failure.
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PMID:Human skeletal muscle digitalis glycoside receptors (Na,K-ATPase)--importance during digitalization. 838 26

Cytosolic free sodium concentration ([Na+]i) was investigated in intact platelets from 5 hypertensive patients with primary aldosteronism (unilateral adenoma in 3 patients, and adrenal hyperplasia in 2 patients) and 21 normotensive control subjects. [Na+]i was measured using a novel sodium-sensitive fluorescent dye technique. [Na+]i was significantly decreased in platelets from patients with primary aldosteronism compared to control subjects (21.9 +/- 4.1 mM vs 35.8 +/- 2.2 mM, mean +/- SEM, P < 0.05). After administration of the mineralocorticoid antagonist spironolactone in 4 patients [Na+]i tended to be higher in platelets although the differences did not reach statistical significance (26.3 +/- 7.2 mM vs 18.2 +/- 2.4 mM, P = 0.125). From the present results it may be concluded that intracellular sodium is decreased by aldosterone-induced activation of Na-K-ATPase. That activation may be partly blocked by spironolactone.
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PMID:Effect of spironolactone on cytosolic free sodium concentration in platelets from hypertensive patients with primary aldosteronism. 838 26

Previous studies have documented decreased levels of platelet sodium, potassium adenosine triphosphatase (Na+, K+ ATPase) enzyme activity in allergic subjects. The purpose of this study was to determine the effect of several drugs used to treat allergy and asthma on platelet Na+,K+ ATPase activity. Platelets from five allergic and five nonallergic subjects were incubated at 37 degrees C for 30 minutes with cortisol (1.0 to 3.6 micrograms/ml), theophylline (10 to 40 micrograms/ml), cromolyn (0.5 to 2.0 micrograms/ml), albuterol (3 to 24 ng/ml), chlorpheniramine (2.5 to 20 micrograms/ml), or diluent. The platelets were then rinsed, sonicated, serially centrifuged, and assayed for Na+,K+ ATPase activity nmol/min x micrograms protein by spectrophotometry. Mean activity (+/- 1 SEM) for the diluent incubation was 5.55 +/- 1.27 nmol/min x micrograms protein and 0.91 +/- 0.32 nmol/min x micrograms protein for the nonallergic and allergic subjects, respectively. The enzyme activity of allergic platelets (same units as above) increased after incubation with the following drugs: cortisol, 6.07 +/- 1.75 (p < 0.025) at 1.0 micrograms/ml, 7.55 +/- 1.36 (p < 0.005) at 1.4 micrograms/ml, and 5.95 +/- 0.91 (p < 0.025) at 1.8 micrograms/ml; cromolyn, 5.79 +/- 1.68 (p < 0.050) at 1.0 micrograms/ml; and albuterol, 4.43 +/- 1.61 (p < 0.05) at 12 ng/ml. Theophylline and chlorpheniramine did not have a similar effect on Na+,K+ ATPase activity. These data show that some of the drugs commonly used to treat allergic patients, especially anti-inflammatory agents, can increase the depressed platelet levels of Na+,K+ ATPase activity observed in allergic subjects. Modulation of Na+,K+ ATPase is a possible mechanism of action for these drugs in vivo.
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PMID:In vitro modulation of platelet sodium, potassium adenosine triphosphatase enzyme activity by antiallergy drugs. 839 60


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