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)

Preparations of lysed synaptosomes exhibit a high affinity Ca2+/Mg2+ ATPase and ATP-dependent Ca2+ accumulation activity, with a Km for Ca2+ congruent to 0.5 microM, close to the cytosolic concentration of Ca2+. When these membrane suspensions were incubated with cholinergic agonists muscarine or oxotremorine (1-20 microM), both Ca2+/Mg2+ ATPase and ATP-dependent CA2+ uptake were inhibited in a concentration-dependent fashion. Atropine alone (0.5-1.0 microM) had no effect on either enzyme or uptake activity, but significantly inhibited the actions of both muscarine and oxotremorine. No significant effects by cholinergic agonists or antagonists were seen on fast or slow phase voltage-dependent Ca2+ channels or Na+-Ca2+ exchange. These results suggest that activation of presynaptic muscarinic receptors produce inhibition of two processes required for the buffering of optimal free Ca2+ by the nerve terminal. Activation of presynaptic muscarinic receptors have been reported to reduce the release of ACh from nerve terminals. Alterations in intracellular free Ca2+ may contribute to a reduction in transmitter (ACh) release seen following activation of cholinergic receptors.
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PMID:Activation of central muscarinic receptors inhibit Ca2+/Mg2+ ATPase and ATP-dependent Ca2+ transport in synaptic membranes. 315 60

Okadaic acid (OA) isolated from black sponge (Halichondria) caused tonic contractions of human umbilical arteries and rabbit aorta both in the presence and absence of Ca2+. This tonic contraction was not affected by Ca2+ chelator, Ca2+ entry blockers and La3+. In addition, the antagonists of alpha-adrenoceptors, histamine, serotonin and ACh receptors had no effect on the OA-induced contraction. High K, ouabain and indomethacin failed to inhibit the response to OA. However, the combination of anaerobic conditions and absence of glucose abolished the response to OA. OA had no effect on the myosin B ATPase and saponin-treated skinned fibers of rabbit aorta. The contractile action of OA may not also be related to calmodulin-related PDE and mitochondrial respiration. In conclusion, although the precise mode of action is not evident at the present time, OA, in its unique pharmacological action--that of producing sustained contraction independent of extracellular Ca2+--may alter the handling of Ca2+ to intracellular store sites.
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PMID:Unique vasocontraction of okadaic acid isolated from black sponge, independent of extracellular Ca2+. 359 72

Nervous or hormonal stimulation of salivary secretion in vivo is associated with a pronounced efflux of K+ from the secretory, acinar cells into the blood. This K+ efflux is followed in the post-stimulus period by a reuptake of K+ into the glandular tissue. In the present study we monitor the changes in [K+] of physiological solutions perfusing a flow chamber containing isolated segments of mouse submandibular glands. Nervous stimulation or the application of exogenous acetylcholine (ACh, 10(-5) M) to the isolated glandular tissue results in characteristic changes in the [K+] of the superfusate, indicating net K+ release followed by K+ reuptake. The post-stimulus reuptake of K+ is shown to be susceptible to blockade by either ouabain (10(-3) M) or piretanide (10(-4) M). The reuptake was markedly attenuated if Cl- in the superfusate was replaced by either NO3- or SO4(2-). The K+ uptake was, however, unaffected when Br- replaced Cl- in the superfusate. Similar effects were observed in the unstimulated glandular tissues. The introduction of Cl-(-)free media containing either NO3- or SO4(2-) resulted in a loss of K+ from the tissue which was followed, upon reintroduction of Cl-, by a pronounced uptake of K+. When Br- was substituted for Cl- there was very little change in [K+] upon removal or reintroduction of Cl-. The uptake of K+ induced by reintroduction of Cl- after a period of NO3- or SO4(2-) superfusion was blocked by both ouabain and piretanide. This uptake of K+ was also dependent on the presence of extracellular Na+. Both Cl- and Na+ had to be present in the superfusing medium for K+ uptake to be fully manifest. These findings indicate that the K+ uptake observed in both the resting and stimulated submandibular gland cannot be explained as solely due to the activity of the Na+-K+-adenosine triphosphatase (Na+-K+-ATPase). The demonstrated anionic selectivity, dependence on extracellular Na+ and susceptibility to blockade by the diuretic piretanide would strongly suggest that a coupled Na+-K+-Cl- co-transport system operates in submandibular glands as it does in other transporting epithelia to achieve K+ uptake.
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PMID:Potassium uptake in the mouse submandibular gland is dependent on chloride and sodium and abolished by piretanide. 379 14

The electrophysiological properties of embryonic chick hearts (ventricles) change during development; the largest changes occur between days 2 and 8. Resting potential (E(m)) and peak overshoot potential (+E(max)) increase, respectively, from -35 mv and +11 mv at day 2 to -70 mv and +28 mv at days 12-21. Action potential duration does not change significantly. Maximum rate of rise of the action potential (+V(max)) increases from about 20 v/sec at days 2-3 to 150 v/sec at days 18-21; + V(max) of young cells is not greatly increased by applied hyperpolarizing current pulses. In resting E(m) vs. log [K(+)](o) curves, the slope at high K(+) is lower in young hearts (e.g. 30 mv/decade) than the 50-60 mv/decade obtained in old hearts, but the extrapolated [K(+)](i) values (125-140 mM) are almost as high. Input resistance is much higher in young hearts (13 M ohm at day 2 vs. 4.5 M ohm at days 8-21), suggesting that the membrane resistivity (R(m)) is higher. The ratio of permeabilities, P(Na)/P(K), is high (about 0.2) in young hearts, due to a low P(K), and decreases during ontogeny (to about 0.05). The low K(+) conductance (g(K)) in young hearts accounts for the greater incidence of hyperpolarizing afterpotentials and pacemaker potentials, the lower sensitivity (with respect to loss of excitability) to elevation of [K(+)](o), and the higher chronaxie. Acetylcholine does not increase g(K) of young or old ventricular cells. The increase in (Na(+), K(+))-adenosine triphosphatase (ATPase) activity during development tends to compensate for the increase in g(K). +E(max) and + V(max) are dependent on [Na(+)](o) in both young and old hearts. However, the Na(+) channels in young hearts (2-4 days) are slow, tetrodotoxin (TTX)-insensitive, and activated-inactivated at lower E(m). In contrast, the Na(+) channels of cells in older hearts (> 8 days) are fast and TTX-sensitive, but they revert back to slow channels when placed in culture.
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PMID:Changes in membrane properties of chick embryonic hearts during development. 426 8

In goose salt gland slices incubated in bicarbonate-buffered medium which contained 170 mEq of Na(+)/liter, net total tissue Na(+), expressed as milliequivalents per kilogram, was, in the presence of either acetylcholine (plus eserine) or ouabain, significantly higher than that of the bathing fluid. Acetylcholine caused an increase in the tissue Na(+) content as compared with untreated slices; there was an approximately equivalent decrease in K(+) and a significant decrease in Cl(-). The calculated net intracellular concentrations of Na(+), expressed as milliequivalents per liter of intracellular water, in unstimulated, acetylcholine-stimulated, and ouabain-treated slices were 2.1, 3.1, and 2.7 times higher, respectively, than the concentration of Na(+) in the bathing fluid. The net intracellular concentration of Na(+), expressed as milliequivalents per liter of intracellular water, in slices incubated in the presence of acetylcholine was 531 mEq/liter; this is approximately the same as the concentration of Na(+) in the secreted fluid of the goose salt gland (515 mEq/liter). The results indicate that the main concentration gradient for Na(+) could be established across the basal membrane. The data do not indicate whether this involves active transport of Na(+) per se. A second stage which might involve Na-K ATPase activity at the luminal membrane is discussed. The sum of the total tissue Na(+) and K(+) was approximately 250 mEq/kg, whereas the Cl(-) content was only approximately 130 mEq/kg.
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PMID:The Na+, and Cl- content of goose salt gland slices and the effects of acetylcholine and ouabain. 606 48

Acetylcholine (ACH) produced specific inhibition of Na, K-ATP-ase activity in sarcolemmic preparations of the frog heart (K0.5 = 1 microM), dog atria (K0,5 = 5 microM) and ventricles (K0.5 = 1 microM), and dog small intestinal smooth muscles (K0,5 = 0.5 microM). K0.5 is the concentration causing a half-maximal effect. Atropine (10(-7) = 10(-6) M) blocked the inhibitory effect of ACH. The preparations contained a considerable number of 3H-quinuclidinyl benzilate (3H-QNB) binding sites. Treatment of atrial sarcolemma with a mixture of digitonin and sodium cholate resulted in a substantial decrease in the number of 3H-QNB binding sites in the membrane, while Na,K-ATPase lost responsiveness to ACH. In the presence of 10 microM GTP there was a noticeable decrease in sensitivity of the enzyme to ACH. It is assumed that inhibition of Na, K-ATPase activity by acetylcholine is mediated by muscarinic receptor activation with the involvement in this process of GTP-binding proteins.
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PMID:[M-cholinoreceptor-mediated inhibition of Na, K-ATPase activity in the myocardial sarcolemma and intestinal smooth muscles by acetylcholine]. 609 7

Acetylcholine does not change the activity of Na, K-ATPase isolated from pig kidney. The enzyme is shown to have insignificant acetylcholinesterase activity. It is suggested that Na, K-ATPase sensitivity to acetylcholine disappears in the course of enzyme purification and that acetylcholinesterase activity is extrinsic.
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PMID:[Cholinergic regulation of the Na, K-ATPase activity of the pig kidney]. 609 43

1. It has been shown that different experimental conditions known to inhibit Na-K-activated ATPase, and enzyme present in the neuronal membranes, are able to promote transmitter release (ACh, NA, etc.) from different tissues, simply by making the membrane leaky. 2. Under physiological conditions, Ca entering the cell transiently inhibits membrane ATPase, resulting in a transient change in membrane permeability and a subsequent release of transmitter. 3. When membrane ATPase inhibitor was used one part of the release proved to be Ca-independent. This finding indicates that the voltage and Ca-dependent link of transmitter release can be by-passed by direct membrane ATPase inhibitors (ouabain). 4. Neurochemical and electrophysiological evidence was obtained on mouse diaphragm that most of the released ACh is cytoplasmic and Na-K ATPase inhibition is responsible for its release. 5. The stimulation of membrane ATPase (by switching off K and its readmission) results in an inhibition of both ACh and noradrenaline release evoked by axonal stimulation. 6. It is suggested that, in those cases where the varicose axon terminals do not make synaptic contact, the transmitter released from the cytoplasmic pool contributes to the transmission, since during diffusion (sometimes few thousand nm) transmitter of different origins becomes mixed up.
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PMID:Na-K activated ATPase and the release of acetylcholine and noradrenaline. 613 50

The aim of the present experiments was to study the effects of the neurotransmitters acetylcholine, noradrenaline, 5-hydroxytryptamine, and dopamine on the Na+,K+-ATPase of rat brain synaptosomal fractions. It is shown that dopamine at low concentrations specifically inhibits the Na+,K+-ATPase of synaptic membranes from the brain regions rich in dopaminergic endings, but has no effect on the synaptosomal Na+,K+-ATPase from the other parts of brain. Acetylcholine and noradrenaline have similar specific effects on Na+,K+-ATPase from cholinergic and adrenergic synaptosomes. The Na+,K+-ATPase of synaptic membranes from the different brain regions, characterised by different distributions of cholinergic, adrenergic, and 5-hydroxytryptaminergic endings, show different reactions with neurotransmitters. These data indicate a functional significance of the effects of the neurotransmitters on the synaptosomal Na+,K+-ATPase.
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PMID:Functional significance of the effects of neurotransmitters on the Na+,K+-ATPase system. 614 22

1 Secretion of catecholamines (CA) evoked by ouabain, chlormadinone acetate (CMA), phenoxybenzamine (Pbz) and vanadate, four agents known to inhibit Na(+), K(+)-dependent Mg(2+)-activated adenosine triphosphatase (ATPase) activity has been studied in suspensions of bovine isolated adrenal medullary cells.2 Acetylcholine (ACh) evoked a 5 fold increase of the basal CA secretion from isolated cells suspended in oxygenated Krebs-bicarbonate solution kept at 27 degrees C. Secretion was antagonized by Ca(2+)-deprivation or hexamethonium, indicating good functional viability of the cells.3 Ouabain (10(-7) to 10(-4) M) evoked a progressive, dose-dependent release of CA from cell suspensions. Study of the time course of the secretory response for 2 h allowed the separation of two components in the secretory response at all doses studied: a slow initial component (0.011 pg/min CA) and a second faster component (0.032 pg/min CA).4 CMA evoked a clear-cut CA secretory response. The ED(50) for CMA was 10(-4) M, as compared to 3 x 10(-6) M for ouabain. Pbz and vanadate did not induce CA release.5 [(3)H]-ouabain was taken up and bound to intact isolated cells by a non-saturable binding process. However, in semi-purified plasma membranes from bovine adrenal medulla a saturable specific [(3)H]-ouabain binding process was observed with a K(D) of 8.1 nM. Binding to the membranes was ATP-dependent and antagonized by K(+).6 [(3)H]-ouabain specific binding to membranes was antagonized by ouabain and CMA, but not by Pbz or vanadate; the ID(50) for ouabain and CMA were 10(-6) and 10(-5) M respectively.7 Ouabain partially inhibited, in a dose-dependent manner, Na(+), K(+)-Mg(2+) ATPase activity of the semi-purified plasma membranes.8 The results demonstrate a good correlation between the ability of different drugs, known to inhibit ATPase activity, to displace [(3)H]-ouabain binding to adreno-medullary plasma membranes and their capacity to evoke a CA secretory response from isolated chromaffin cells. The data also suggest that the CA secretory effects of ouabain may not be due simply to inhibition of the Na(+) pump and the subsequent ionic redistribution across the plasma membrane; a second mechanism may also be involved.
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PMID:Correlation between catecholamine secretion from bovine isolated chromaffin cells and [3H]-ouabain binding to plasma membranes. 616 27


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