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 effect of blockade of ouabain-sensitive alpha 2 and alpha 3 (neural type) isozymes of Na+, K(+)-ATPase was investigated on frog neuromuscular preparations by recording the frequency augmentation-potentiation (FAP) of the endplate potential, an electrophysiological and neuropharmacological technique to analyze the drug actions on the release process of the readily releasable transmitter quanta. Erythrosin B, which was thought to selectively inhibit the neural type Na+, K(+)-ATPase, pivoted the log-linear FAP relation counterclockwise without altering the intercept on the ordinate. Chlormadinone had a similar action. An increase in the concentration of extracellular K+ ions pivoted the FAP relation clockwise with a concomitant upward shift of the intercept on the ordinate, and low K+ Ringer's solution produced an inverse effect. In contrast, Li+ ions shifted the FAP relation upwards dose-dependently leaving its slope unchanged. Cinnarizine, a blocker for inositol-1,4,5-trisphosphate-induced Ca2+ release, and 5,5'-dimethyl-1,2-bis(2-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid, a specific intracellular Ca2+ chelator, significantly antagonized the potentiating action of Li+. The ouabain-sensitive neural type Na+, K(+)-ATPase isozyme, which is abundant in neural tissues, seems to play an important role in stimulation frequency-dependent modulation of the quantal transmitter release such as FAP.
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PMID:Effects of inhibitors of ouabain-sensitive Na+, K(+)-ATPase and Li+ ions on the neuromuscular transmission of the frog. 747 24

During the first few minutes following traumatic brain injury, cells are exposed to an indiscriminate release of glutamate from nerve terminals resulting in a massive ionic flux (e.g., K+ efflux) via stimulation of excitatory amino acid (EAA)-coupled ion channels. The present study was undertaken to elucidate the causal relationship between these ionic shifts and lactate accumulation in the injured brain, by examining the effects of ouabain (an inhibitor of Na+/K+-ATPase), Ba2+ (an inhibitor or non-energy-dependent glial K+ uptake) and kynurenic acid (KYN; a broad-spectrum EAA antagonist) on lactate accumulation. Two microdialysis probes were placed bilaterally in the rat parietal cortex. One was perfused with a test drug (1.0 mM ouabain, 2.0 mM Ba2+ or 10 mM KYN) and the other with Ringer's solution (control) for 30 min prior to injury. Following a 2.2-2.7 atm fluid-percussion injury, lactate levels in the dialysate increased (up to 116.6% above baseline) for the first 16 min and returned to baseline levels within 20 min after injury. This lactate accumulation was attenuated by preinjury administration of ouabain and KYN and was prolonged by Ba2+ administration. These findings indicate that lactate accumulations following concussive brain injury is a result of increased glycolysis which supports ion-pumping mechanisms, thereby, restoring the ionic balance which was disrupted by stimulation of EAA-coupled ion channels.
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PMID:Lactate accumulation following concussive brain injury: the role of ionic fluxes induced by excitatory amino acids. 754 Sep 25

We performed experiments to elucidate the calcium influx pathways in freshly dispersed rabbit corneal epithelial cells. Three possible pathways were considered: voltage-gated Ca++ channels, Na+/Ca++ exchange, and nonvoltage-dependent Ca(++)-permeable channels. Whole cell inward currents carrying either Ca++ or Ba++ were not detected using voltage clamp techniques. We also used imaging technology and the Ca(++)-sensitive ratiometric dye fura 2 to measure changes in intracellular Ca++ concentration ([Ca]i). Bath perfusion with NaCl Ringer's solution containing the calcium channel agonist Bay-K-8644 (1 microM), or Ni++ (40 microM), a blocker of many voltage-dependent calcium channels, did not affect [Ca++]i. Membrane depolarization with a KCl Ringer's bath solution resulted in a decrease in [Ca++]i. These results are inconsistent with the presence of voltage gated Ca++ channels. Nonvoltage gated Ca++ entry, on the other hand, would be reduced by membrane depolarization and enhanced by membrane hyperpolarization. Agents which hyperpolarize via stimulation of K+ current, such as flufenamic acid, resulted in an increase in ratio intensity. The cells were found to be permeable to Mn++ and bath perfusion with 5 mM Ni++ decreased [Ca++]i suggesting that the Ca++ conductance was blocked. These results are most consistent with a nonvoltage gated Ca++ influx pathway. Finally, replacing extracellular Na+ with Li+ resulted in an increase in [Ca++]i if the cells were first Na(+)-loaded using the Na+ ionophore monensin and ouabain, a Na(+)-K(+)-ATPase inhibitor. These results suggest that Na+/Ca++ exchange may also regulate [Ca++]i in this cell type.
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PMID:Calcium entry in rabbit corneal epithelial cells: evidence for a nonvoltage dependent pathway. 754 Oct 85

1. The aim of this study was to elucidate if the K+ uptake was higher in cultured human glioma cells than in cells from other malignant tumors and to analyze the importance of membrane potential and K+ channels for the uptake. 2. K+ transport properties were studied with the isotopes 42K and the K-analogue 201Tl. 3. Comparison with cultured cells from other malignant tumors showed that the specific steady-state accumulation of Tl+ was significantly higher in glioma cells (U-251MG and Tp-378MG). 4. In Ringer's solution at 37 degrees C the rates of K+ and Tl+ uptake were both inhibited by about 55% in ouabain and 60% in furosemide, bumetanide, or Na(+)- or Cl(-)-free medium. This indicated that the routes for K+ and Tl+ uptake were similar and due to Na,K-ATPase-dependent transport and to Na-K-Cl cotransport. 5. About 10% of the uptake was neither ouabain nor bumetanide sensitive. Ba2+, which is known to block inward-rectifying K+ channels and to depolarize glial cells, and other K+ channel blockers (Cs+ and bupivacaine), had no effect on Tl+ uptake. 6. Metabolic inhibition with dinitrophenol reduced the uptake rate to 17%. 7. The washout of Tl+ was unaffected by bumetanide and K+ channel blockers, but dinitrophenol caused a transient increase of 75%, an effect which persisted in the presence of K+ channel blockers. 8. It was concluded that the high specific K+ and Tl+ accumulation in cultured human glioma cells was due not to the presence of inwardly rectifying K+ channels or other identified K+ channels, but to Na,K-ATPase dependent transport and Na-K-Cl cotransport.
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PMID:Mechanism of high K+ and Tl+ uptake in cultured human glioma cells. 755 34

There is evidence that intracellular Na+ entry potentiates hypoxic-ischemic cell death by causing cytotoxic cell edema, intracellular acidosis, and gating of Ca2+ entry by reverse activation of the Na(+)-Ca2+ exchanger. In this study, we examined the role of Na+ in mediating traumatic injury to spinal cord axons. Dorsal column segments from adult rats (n = 87) were isolated and maintained in an in vitro recording chamber while being superfused with oxygenated Ringer's solution (95% O2/5% CO2, 25 degrees C). Selected experiments (n = 10) also were done at 33 degrees C. Compound action potentials (CAP) were recorded from microelectrodes. Injury was performed by compression of the dorsal column segment for 15 sec with a modified aneurysm clip exerting a closing force of 2 gm. With injury, the CAP decreased to 72.1 +/- 9.6% of baseline values. Removal of extracellular Na+ and replacement with the impermeant cation N-methyl-D-glucamine enhanced recovery of the CAP to 98.3 +/- 18.3% (p < 0.05) of baseline. The Na+ channel blockers tetrodotoxin and procaine also improved recovery of the CAP to 96.3 +/- 23.7% (p < 0.05) and 82.8 +/- 4.6% (p < 0.05) of baseline values, respectively. In contrast, increasing Na+ permeability with veratridine resulted in greater attenuation of CAP amplitude after 1 hr of trauma (60.1 +/- 8.4%, p < 0.05). Similarly, prevention of extrusion of Na+ from the intracellular compartment by inhibiting the Na(+)-K(+)-ATPase pump with ouabain resulted in greater attenuation of CAP amplitude at 1 hr after trauma (56.7 +/- 3.6%, p < 0.05). The Na(+)-H+ exchange blockers amiloride (100 microM) and harmaline (100 microM) significantly improved recovery after injury to 89.6 +/- 17.0% (p < 0.05) and 85.7 +/- 7.2% (p < 0.05) of baseline, respectively. However, administration of the Na(+)-Ca2+ exchange blockers benzamil (100 or 500 microM) and bepridil (50 microM) was ineffective. In summary, reduction of extracellular Na+ confers neuroprotection after spinal cord injury in vitro. Intracellular sodium rises appear to be mediated by voltage-gated Na+ channels. Blockade of the Na(+)-H+ exchanger also is neuroprotective, possibly by reducing intracellular acidosis. Furthermore, prevention of extrusion of intracellular Na+ by the Na(+)-K(+)-ATPase pump exacerbates the effects of compression trauma. However, reverse operation of the Na(+)-Ca2+ exchanger does not explain the injurious effects of Na+ in traumatically injured CNS white matter.
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PMID:Mechanisms of secondary injury to spinal cord axons in vitro: role of Na+, Na(+)-K(+)-ATPase, the Na(+)-H+ exchanger, and the Na(+)-Ca2+ exchanger. 855 38

1. When added to the Na(+)-containing solution bathing the isolated toad skin, dinitrophenol (DNP, an uncoupler of oxidative phosphorilation) caused decreases in the baseline values of short circuit current (SCC) and transepithelial conductance (G). 2. DNP also inhibited the increases in SCC and G caused by theophylline, whether added prior to the xanthine, or after the effect of the latter was fully developed. 3. In skins exposed to theophylline and bathed in Cl(-)-free (sulfate Ringer's) solution, the changes in SCC and G had a similar time course (t1/2 > 15 min). In the presence of Cl- (skins bathed in Ringer's solution), SCC decreased with a similar rate, whereas the rate of the decrease in G was greater (t1/2 < 15 min). 4. DNP also decreased the SCC induced by a Cl- concentration gradient in skins exposed to theophylline (SCCg) with a time course similar to its effect on the theophylline-increased G in the presence of Cl-. DNP was effective irrespective of the presence of ambient Na+. 5. A similar difference was observed in skins bathed in CIR and exposed to forskolin. In contrast to theophylline, however, forskolin partially overcame the inhibition of G brought about by DNP; no such recovery was observed in SCC. 6. In contrast to its influence on the responses to theophylline and forskolin, DNP failed to prevent either the increase in G or the onset of SCCg in skins exposed to dibutyryl cyclic AMP. 7. Rotenone, an inhibitor of the electron-transport chain, significantly decreased SCC and G in the unstimulated skin. It also prevented the SCC response to theophylline, and decreased it if added after the effects of the xanthine were fully developed, but failed to modify the increase in G brought about by theophylline. The time course of SCC inhibition by rotenone was similar to that caused by DNP. 8. Ouabain, an inhibitor of Na+,K(+)-ATPase, decreased SCC in the theophylline-stimulated skin, without affecting G. 9. We conclude that, whereas integrity of oxidative energy metabolism is necessary to sustain SCC in the isolated toad skin, it is not a strict requirement for the increase of Cl(-)-dependent G activated by cAMP. 10. The effect of DNP on Cl(-)-dependent G activated by cAMP is probably exerted at the cAMP generation step, by inhibition of adenyl cyclase and/or a decrease in the availability of ATP.
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PMID:Metabolic inhibition and chloride transport in isolated toad skin. 933 86

Net proton secretion and unidirectional chloride fluxes were measured in isolated skin of toads ( Bufo bufo) and frogs ( Rana esculenta) mounted in an Ussing chamber and exposed to a Ringer's solution on the serosal side and a freshwater-like solution (1-3 mM Cl(-)) on the external side. Active proton secretion was 34.2+/-2.0 pmol.cm(-2).s(-1) ( n=18) in frog skin, and 16.7+/-1.7 pmol.cm(-2).s(-1) ( n=10) in toad skin. Proton secretion by toad skin was dependent on the transepithelial potential ( V(T)), and an amiloride-insensitive short-circuit current was stimulated by exogenous CO(2)/HCO(3)(-), indicating the presence of a rheogenic proton pump. Cl(-) influx was 37.4+/-7.5 pmol.cm(-2).s(-1) ( n=14) in frog skin and 19.5+/-3.5 pmol.cm(-2).s(-1) ( n=11) in toad skin. In toad skin, the mean Cl(-) flux ratio was larger than expected for simple electro-diffusion. In 8 of 11 sets of paired skins, influx was greater than the efflux indicating active uptake of Cl(-). Cl(-) influx in toad skin was unaffected by large perturbations (100-150 mV) of V(T), which was accomplished by adding amiloride to the outer bath under open circuit conditions. A component of the Cl(-) efflux seemed to be dependent on V(T). 4,4'-Diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS; 0.3 mM or 1.3 mM) inhibited Cl(-) influx and, surprisingly, increased Cl(-) efflux in toad skin. Influx and efflux of Cl(-) in toad skin were highly dependent on the external [Cl(-)] in the freshwater range (0.1-4 mM). (36)Cl(-) influx decreased whereas the total Cl(-) efflux increased as a function of external [Cl(-)]. These data indicate the presence of a DIDS-sensitive, electroneutral carrier mechanism with an external binding site for Cl(-). Ethoxzolamide (100 micro M), an inhibitor of carbonic anhydrase, reduced proton secretion and Cl(-) influx in frog skin. Concanamycin A (0.1-10 micro M), a specific vacuolar-type proton pump (V-ATPase) inhibitor, significantly reduced proton secretion in frog skin. In addition, concanamycin A (1 micro M) significantly reduced Cl(-) influx in frog skin. We suggest that the active proton secretion and Cl(-) influx are coupled. We hypothesise that an apical V-ATPase is capable of energising active Cl(-) uptake in fresh water by creating a favourable gradient for an apical HCO(3)(-) exit in exchange for external Cl(-). The data also suggest that a carbonic anhydrase activity provides H(+) and HCO(3)(-) for apically co-expressed proton pumps and Cl(-)/HCO(3)(-) exchangers.
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PMID:Proton pump activity is required for active uptake of chloride in isolated amphibian skin exposed to freshwater. 1219 12

Changes in intracellular Ca(2+) concentration control many essential cellular functions like the contraction of smooth muscle cells. The aim of this study was to investigate if the tachykinin substance P (SP) engages external Ca(2+)-sources, internal Ca(2+)-sources, or both in the contraction of the gastrointestinal smooth muscle of rainbow trout (Oncorhynchus mykiss) and the African clawed frog (Xenopus laevis). Strip preparations made of either longitudinal smooth muscle of proximal intestine or circular smooth muscle of cardiac stomach were mounted in organ baths and the tension was recorded via force transducers. Ca(2+)-free Ringer's solution containing the Ca(2+) chelating agent EGTA (2mM) abolished all spontaneous contractions. Exposure to SP in Ca(2+)-free solution decreased the response. Preparations were also treated with the Ca(2+)-ATPase inhibitor thapsigargin (10 microM) during 30 min. Thapsigargin reduced the effect of SP on intestinal longitudinal smooth muscle in rainbow trout and on stomach circular smooth muscle in the African clawed frog and to a less extent in the intestinal longitudinal smooth muscle. The results show that external Ca(2+) is of great importance, but is not the only source of Ca(2+) recruitment in SP-activation of gastrointestinal smooth muscle in rainbow trout and the African clawed frog.
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PMID:Ca2+-recruitment in tachykinin-induced contractions of gut smooth muscle from African clawed frog, Xenopus laevis and rainbow trout, Oncorhynchus mykiss. 1267 95

Through subtractive hybridization, H+/K+-ATPase beta subunit mRNA, highly expressed in the larval stomach of Xenopus laevis, was isolated. In situ hybridization demonstrated that the H+/K+-ATPase beta subunit mRNA was exclusively expressed in manicotto gland cells of the larval stomach, not in any other cell. Northern blot analysis showed that metamorphosis-associated changes of the H+/K+-ATPase beta subunit mRNA expression in the stomach were characterized by high expression in tadpoles, a considerably lower expression in metamorphosing tadpoles, and a re-increase of expression in froglets. Further in situ hybridization showed that the decrease of expression correlated with the degeneration of larval type epithelium in the manicotto gland, while the re-increase correlated with the differentiation of oxynticopeptic cells of the adult type stomach. Moreover, the H+/K+-ATPase beta subunit mRNA was expressed in adult epithelial primordia. Such changes were found in thyroid hormone-induced precocious metamorphosis. Based on studies using this ATPase as well as xP1 and PgC (pepsinogen C) as molecular markers, this study discusses a probable cell lineage involved in metamorphosis-associated stomach remodeling. The pH of luminal contents of the larval stomach was found to be lower than 2. In addition, the pH of an isolated stomach changed from 7.2 to lower than 4 after incubation in Ringer's solution, suggesting acid production from the larval stomach. This is the first demonstration of the H+/K+-ATPase-mediated acid production and secretion in the larval stomach of Xenopus laevis.
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PMID:Stomach remodeling-associated changes of H+/K+-ATPase beta subunit expression in Xenopus laevis and H+/K+-ATPase-dependent acid secretion in tadpole stomach. 1556 47

Cell volume regulation was investigated in gastric surface epithelial cells during hypertonic conditions. Isolated Necturus antral mucosa was perfused on the serosal side with Ringer's solution (pH 7.25, 95%O2/5%CO2) and on the mucosal side successively with 150-500 mM NaCl. Amiloride, ouabain, and bumetanide were used to experimentally inhibit Na+/H+, Na+/K+ ATPase or Na+-K+-2Cl- ion transporters. Intracellular sodium activity and cell volume changes were measured with liquid sensor microelectrodes. The increase in intracellular sodium activity caused by luminal hyperosmolar exposure was mainly due to cell shrinkage. Inhibition of Na+/K+ ATPase or Na+-K+-2Cl- cotransporter increased hyperosmotic cell shrinkage (-52 +/- 5%, -85 +/- 19%, and -77 +/- 9% for control, ouabain, and bumetanide, respectively). Inhibition of Na+/K+ ATPase increased intracellular sodium activity (from 18 +/- 4 to 52 +/- 12 mM). Cell volume regulation in gastric epithelial surface cells during mucosal hyperosmolar exposure is maintained by the basolateral Na+-K+-2Cl- cotransporter, while Na+/K+ ATPase maintains sodium balance, but Na+/H+ antiport seems to have a less important role.
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PMID:Cell volume regulation during hyperosmotic shrinkage is mediated by Na+/K+-ATPase and Na+-K+-2Cl- cotransporter in Necturus gastrics surface epithelial cells. 1624 Feb 13


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