Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of the alpha 1-adrenergic agonist phenylephrine (PE) and the phorbol ester 4 beta-phorbolmyristate-acetate (PMA) on sodium pump function were studied in the rat liver. In order to distinguish between direct and indirect influences, ouabain-sensitive 86Rb uptake by intact liver slices was compared with ouabain-sensitive Na+/K+-ATPase activity in plasma membranes isolated from PE and PMA-perfused livers. At a buffer Ca2+ level of 2.5 mmol/l, PE (10 mumol/l) caused an initial stimulation of both 86Rb uptake and Na+/K+-ATPase activity followed at 5 min by a decrease in both activities. Both actions were blocked by the alpha 1-antagonist prazosin. The decrease in ouabain-sensitive Na+/K+-ATPase was paralleled by an increase in Mg2+ ATPase activity. At a Ca2+ level of 1.5 mmol/l, PE stimulation of 86Rb uptake and Na+/K+-ATPase was sustained, and the inhibitory component was not expressed. PMA (4 mumol/l) reduced 86Rb uptake and Na+/K+-ATPase and similar to PE, this inhibition was paralleled by an increase of Mg2+-ATPase activity. 4 alpha-PMA, which does not activate protein kinase C, failed to influence 86Rb uptake or Na+/K+-ATPase. These results demonstrate that PE and PMA effects on ouabain-sensitive 86Rb uptake are preserved in isolated membranes, indicating a direct influence on the Na+/K+-ATPase. A role for protein kinase C in modulating sodium pump activity is suggested.
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PMID:Influence of alpha 1-adrenergic receptor stimulation and phorbol esters on hepatic Na+/K+-ATPase activity. 290 84

The sodium pump, (Na+ + K+)-ATPase, which is involved in the transport of cations and water movement by the colonic mucosa, may be decreased in various diarrhoeal states. In this study, we have measured 3H-ouabain binding and (Na+ + K+)-ATPase activity in human colonic biopsy homogenates and the influence of various inflammatory and antiinflammatory compounds on these parameters. 3H-ouabain binds to one site of high affinity (KD 1.9 +/- 0.2 X 10(-9) mol/l) with a maximal binding capacity of 7.5 +/- 0.8 X 10(14) binding sites/g protein. Both arachidonic and linoleic acid inhibited (Na+ + K+)-ATPase activity (IC50 arachidonic acid: 7.5 X 10(-5) mol/l, linoleic acid: 6.5 X 10(-5) mol/l) and Mg2+-ATPase activity (IC50 arachidonic acid: 9 X 10(-5) mol/l, linoleic acid: 4 X 10(-5) mol/l). Arachidonic acid inhibited 3H-ouabain binding, (IC50 3.2 X 10(-5) mol/l). The following antiinflammatory compounds, at concentrations up to 1 X 10(-3) mol/l, did not influence ATPase activity directly nor reverse the arachidonic acid-induced inhibition: indomethacin (cyclooxygenase inhibitor), nordihydroguaiaretic acid (lipoxygenase inhibitor), sulphasalazine and its metabolites: 5-aminosalicylic acid, N-acetylaminosalicylic acid and sulphapyridine. These results indicate that human colonic (Na+ + K+)-ATPase is inhibited by the prostanoid precursors, arachidonic and linoleic acid. From a therapeutic point of view (effect on colonic (Na+ + K+)-ATPase and perhaps diarrhoea), the suppression of the production of these prostanoid precursors by drugs may, therefore, be beneficial in the treatment of inflammatory bowel disease.
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PMID:Inhibition of human colonic (Na+ + K+)-ATPase by arachidonic and linoleic acid. 301 58

The distribution of plasma membrane markers, the sodium pump [evaluated as ouabain-sensitive, potassium-stimulated p-nitrophenyl phosphatase (K+-pNPPase)], [3H]saxitoxin binding, and 5'-AMPase, was studied in the subcellular fractions prepared from the homogenates of the longitudinal smooth muscle/myenteric plexus of dog ileum. The K+-pNPPase activity and [3H]-saxitoxin binding were found to be predominantly associated with the synaptosomal fraction as indicated by the high level of these activities in the crude synaptosomal fraction and by the copurification of K+-pNPPase and [3H]saxitoxin binding, but not 5'-AMPase, with several synaptosomal markers during the fractionation of the crude synaptosomal fraction on density gradients. In contrast to the K+-pNPPase activity and [3H]saxitoxin binding, the 5'-AMPase activity was found to be concentrated in the microsomal pellet. Further fractionation of microsomes on density gradient resulted in copurification of 5'-AMPase but not K+-pNPPase or [3H]saxitoxin binding, with other smooth muscle plasma membrane-bound enzymes, such as high-affinity Ca2+-ATPase, Mg2+-ATPase, and Ca2+-ATPase. It was concluded that in the longitudinal smooth muscle/myenteric plexus, the sodium pump activity is present in higher density in the neuronal plasma membranes whereas 5'-AMPase activity is concentrated in the smooth muscle plasma membranes.
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PMID:Subcellular fractionation of the longitudinal smooth muscle/myenteric plexus of dog ileum: dissociation of the distribution of two plasma membrane marker enzymes. 304 Sep 6

Because it has been suggested that decreased activity at the erythrocyte sodium pump might be the cause of age-related decreases in basal oxygen consumption, we have examined age-associated changes in Na+,K+-ATPase activity in red cell membranes. The initial portion of this study was directed toward elucidating possible methodological pitfalls in membrane preparation which might account for some of the variable results reported in prior erythrocyte Na+,K+-ATPase studies. We found that two of four red cell membrane fractions have substantial Mg2+-ATPase activity and contribute a significant portion of total membrane protein. As these two fractions contain little Na+,K+-ATPase activity their contamination of the other two fractions could cause significant variation in measured Na+,K+-ATPase activity. Additionally, we found that meal feeding raised Na+,K+-ATPase activity necessitating that measurements be made in the fasting state. With these methodological variables controlled, we found only a 10.8% coefficient of variation between fasting samples obtained on separate days in eight subjects. Using this methodology, we observed no correlation of Na+,K+-ATPase specific activity with age in males, and only a weak correlation in females who showed decreasing Na+,K+-ATPase specific activity occurring with advancing age. These observations suggest that changes in erythrocyte Na+,K+-ATPase activity do not cause the age-related fall in basal oxygen consumption.
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PMID:Variables affecting measurement of human red cell Na+,K+ATPase activity: technical factors, feeding, aging. 614 85

Neurotensin is a peptide present in mammalian CNS and peripheral tissues, which may play a major role in neurotransmission or neuromodulation, subserving diverse physiological functions. We studied the effect of added neurotensin on ATPase activities in synaptosomal membranes isolated from rat cerebral cortex. Neurotensin at 3 x 10(-8)-3 x 10(-6) M concentration decreased 20-44% Na+,K+-ATPase activity but failed to modify Mg2+-ATPase activity; lower neurotensin concentrations (3 x 10(-14)-3 x 10(-10) M) had no effect on enzyme activities. This inhibitory effect was abolished by neurotensin heating, by enzyme preincubation with neurotensin during periods exceeding 10 min, or by adding 1 x 10(-6) M SR 48692, a high affinity neurotensin receptor antagonist. Levocabastine, which blocks low affinity neurotensin receptor, failed to alter enzyme inhibition by the peptide. It is suggested that the sodium pump may be a target for neurotensin effects at neuronal level involving the participation of high affinity neurotensin receptor.
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PMID:Neurotensin inhibits neuronal Na+,K+-ATPase activity through high affinity peptide receptor. 1082 14

Effect of calix[4]arenes C-97, C-99, C-107, functionalized by fragments of alpha-hydroxy-phosphonic, alpha-aminophosphonic- and methylene-bisphosphonic acid on enzymatic activity of oubaine-sensitive Na+, K+-ATPase and oubaine-resistant basal Mg2+- ATPase (specific activity - 10.6 +/- 0.9 and 18.1 +/- 1.2 micromol Pi/h per 1 mg of protein, respectively; n = 7) was studied in experiments made on the suspension of myometrium cell plasma membranes treated by 0.1% solution of digitonin. It was found that calixarene-phosphonic acids in concentration of 100 microM inhibited enzymatic activity of Na+, K+-ATPase by 86-98% and did not practically affect activity of Mg2+-ATPase. These calixarenes were more efficient than oubaine in suppressing enzymatic activity of the sodium pump: in case of the effect of calixerenes the value of the appearence constant of inhibition I0.5 was < 0.1 microM. Calixarene-methylene-bisphosphonic acid (calixarene C-97; I0.5 =33 +/- 4 microM (n = 6) takes the most efficient inhibitory effect on Na+,K+-ATPase activity among the studied calixarenes. A phenomenon of negative cooperation: the Hill coefficient value etaH =0.1-0.5<1 is characteristic of both the inhibiting effect of calixarenes and oubaine. Reguliarities of calixarenes C-97 effect on enzymatic activity of Na+,K+-ATPase were studied. As it appeared its inhibiting effect cannot be caused by trivial factors - potentially possible binding of Mg ions by it and (or) this substance effect on Mg2+ interaction with ATP4- in the incubation medium. Calixerene C-97 does not also decrease the enzyme affinity for Mg ions or ATP. However this calixerenes decreases the affinity of Na+,K+-ATPase for Na ions (the value of activation constant K(Na+)) from 50 +/- 4 (control) to 76 +/- 6 microM in the control and under the effect of calixerene, respectively). A conclusion is made that calixerene C-97 is highly-efficient (with respect to oubaine) and selective (with respect to lack of its effect on basal Mg2+-ATPase) inhibitor of Na+,K+-ATPase of plasma membrane. In the practical aspect it may be used in concentration of 1-10 microM in biochemical membranology when testing and studying kinetic and catalytic properties of the sodium pump in case of such experimental model, as the plasma membrane fraction.
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PMID:[Effect of calixarene-phosphonic acid on Na+, K+-ATPase activity in plasma membranes of the smooth-muscle cells]. 1714 69

In the experiments carried out with the suspension of the myometrium cell plasmatic membranes treated with 0.1% digitonin solution the authors investigated influence of the calix[4]arenes C-97 and C-107 (codes are shown) on ouabain effect on the Na+,K+-ATPase activity. It was shown that calixarenes in concentration 100 tiM inhibited by 97-98% the enzymatic Na+,K+-ATPase activity, while they did not practically influence on the basal Mg2+-ATPase activity, and suppressed much more effective than ouabain the sodium pump enzymatic activity: in the case of the action of the calixarenes the value of the apparent constant of inhibition I0.5 was < 0.1 microM while for ouabain it was 15-25 microM. The negative cooperative effect was typical of the inhibitory action of calixarenes, as well as ouabain: the value of Hills factor nH = 0.3-0.5 <1. The modelling compound M-3 (0.1 microM 4 microM)--a fragment of the calixarene C-107--did not practically influence the enzymatic activities as Na+,K+-ATPase and basal Mg2+-ATPase. Hence the influence of calixarene C-107 on the Na+, K+-ATPase activity is caused by cooperative action of two fragments M-3 and effect of calixarene bowl, rather than by simple action of the fragment M-3. Calixarenes C-97 and C-107, used in concentration corresponding to values of I0.5 (40 and 60 nM, accordingly), essentially stimulated inhibiting action of ouabain on the specific Na+, K+-ATPase activity in the memrane fraction. Under coaction of ouabain with calixarene C-97 or C-107 there was no additive effect of the action of these inhibitors on the Na+,K+-ATPase activity. Calixarene C-97 brought in the incubation medium in concentration of 10 nM not only led to inhibition of the Na+,K+-ATPase activity relative to control, but also simultaneously increased the affinity of the enzyme for the cardiac glycoside: the magnitudes of the apparent constant of inhibition I0.5 were 21.0 +/- 5.2 microM and 5.3 +/- 0.7 microM. It is concluded, that highly effective inhibitors of the Na+,K+-ATPase activity--calixarenes C-97 and C-107 can enhance the effect of the sodium pump conventional inhibitor--ouabain, increasing the affinity of the enzyme for the cardiac glycoside (on the example of calixarene C-97).
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PMID:[The calixarenes C-97 and C-107 stimulate influence of ouabain on the Na+,K+-ATPase activity in plasmatic membrane of smooth muscle cells]. 1749 19