• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.2
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• pp.352-367
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• 1998

Intracellular pH (pHi) plays an important role in the regulation of cellular processes by influencing the acitivity of various enzymes in cells. Therefore, almost every type of mammalian cell possesses an ability to regulate its pHi. One of the most prominent mechanisms in the regulation of pHi is $Na^+/H^+$ exchanger. This exchanger has been known to be activated when cells are stimulated by the binding of agonist to the muscarinic receptors. Therefore, the aims of this study were to compare the rates of $H^+$ extrusion through $Na^+/H^+$ exchanger before and during muscarinic stimulation and to investigate the possible existence of $HCO_3^-$ transporter which is responsible for the continuous supply of $HCO_3^-$ ion to saliva. Acinar cells were isolated from the rat mandibular salivary glands and loaded with pH-sensitive fluoroprobe, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein(BCECF), for 30min at room temperature. Cells were attached onto the coverglass in the perfusion chamber and the changes in pHi were measured on the iverted microscope using spectrofluorometer. 1. By switching the perfusate from $HCO_3^-$-free to $HCO_3^-$-buffered solution, pHi decreased by $0.39{\pm}0.02$ pH units followed by a slow increase at an initial rate of $0.04{\pm}0.007$ pH units/min. The rate of pHi increase was reduced to $0.01{\pm}0.002$ pH units/min by the simultaneous addition of 1 mM amiloride and $100{\mu}M$ DIDS. 2. An addition and removal of $NH_4^+$ caused a decrease in pHi which was followed by an increase in pHi. The increase of pHi was almost completely blocked by 1mM amiloride in $HCO_3^-$-free perfusate which implied that the pHi increase was entired dependent on the activation of $Na^+/H^+$ exchanger in $HCO_3^-$-free condition. 3. An addition of $10{\mu}M$ carbachol increased the initial rate of pHi recovery from $0.16{\pm}0.01$ pH units/min to $0.28{\pm}0.03pH$ units/min. 4. The initial rate of pHi decrease induced by 1mM amiloride was also increased by the exposure of the acinar cells to $10{\mu}M$ carbachol ($0.06{\pm}0.008pH$ unit/min) compared with that obtained before carbachol stimulation ($0.03{\pm}0.004pH$ unit/min). 5. The intracellular buffering capacity ${\beta}1$ was $14.31{\pm}1.82$ at pHi 7.2-7.4 and ${\beta}1$ increased as pHi decreased. 6. The rate of $H^+$ extrusion through $Na^+/H^+$ exchanger was greatly enhanced by the stimulation of the cells with $10{\mu}M$ carbachol and there was an alkaline shift in the activity of the exchanger. 7. An intrusion mechanism of $HCO_3^-$ was identified in rat mandibular salivary acinar cells. Taken all together, I observed 3-fold increase in $Na^+/H^+$ exchanger by the stimulation of the acinar cells with $10{\mu}M$ carbachol at pH 7.25. In addition, I have found an additional mechanism for the regulation of pHi which transported $HCO_3^-$ into the cells.

• The Korean Journal of Physiology and Pharmacology
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• v.26 no.3
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• pp.219-225
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• 2022

Glucagon like peptide-1 (GLP-1) released from enteroendocine L-cells in the intestine has incretin effects due to its ability to amplify glucose-dependent insulin secretion. Promotion of an endogenous release of GLP-1 is one of therapeutic targets for type 2 diabetes mellitus. Although the secretion of GLP-1 in response to nutrient or neural stimuli can be triggered by cytosolic Ca²⁺ elevation, the stimulus-secretion pathway is not completely understood yet. Therefore, the aim of this study was to investigate the role of reverse Na⁺/Ca²⁺ exchanger (rNCX) in Ca²⁺ entry induced by muscarinic stimulation in NCI-H716 cells, a human enteroendocrine GLP-1 secreting cell line. Intracellular Ca²⁺ was repetitively oscillated by the perfusion of carbamylcholine (CCh), a muscarinic agonist. The oscillation of cytosolic Ca²⁺ was ceased by substituting extracellular Na⁺ with Li⁺ or NMG⁺. KB-R7943, a specific rNCX blocker, completely diminished CCh-induced cytosolic Ca²⁺ oscillation. Type 1 Na⁺/Ca²⁺ exchanger (NCX₁) proteins were expressed in NCI-H716 cells. These results suggest that rNCX might play a crucial role in Ca²⁺ entry induced by cholinergic stimulation in NCI-H716 cells, a GLP-1 secreting cell line.

• Molecules and Cells
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• v.28 no.2
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• pp.81-85
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• 2009

$Na^+-H^+$ exchanger (NHE) is the main acid extruder in cardiac myocytes. We review the experimental findings of ion-dependency of NHE activity, and the mathematical modeling developed so far. In spite of extensive investigation, many unsolved questions still remain. We consider that the precise description of NHE activity with mathematical models elucidates the roles of NHE in maintaining ionic homeostasis, especially under pathophysiological conditions.

• YAKHAK HOEJI
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• v.55 no.3
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• pp.247-250
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• 2011

An increase in ventricular pressure can alter cardiac excitation and contraction. Recent report has demonstrated that fluid pressure (FP) suppresses L-type $Ca^{2+}$ current with acceleration of the current inactivation in ventricular myocytes. Since the L-type $Ca^{2+}$ channels known to be regulated by intracellular pH ($pH_i$), this study was designed to explore whether pressurized fluid flow affects pHi in isolated rat ventricular myocytes. A flow of pressurized (~16 dyne/$cm^2$) fluid, identical to that bathing the myocytes, was applied onto single myocytes, and intracellular $H^+$ concentration was monitored using confocal $H^+$ imaging. FP significantly decreased $pH_i$ by $0.07{\pm}0.01$ pH units (n=16, P<0.01). Intracellular acidosis enhances the activity of $Na^+-H^+$ exchanger (NHE). Therefore, we examined if the NHE activity is increased by FP using the NHE inhibitor, HOE642. Although HOE642 did not alter $pH_i$ in control conditions, it decreased $pH_i$ in cells pre-exposed to FP, suggesting enhancement of NHE activity by FP. In addition, FP-induced intracellular acidosis was larger in cells pre-treated with HOE642 than in cells under the control conditions. These results suggest that FP induces intracellular acidosis and that NHE may contribute to extrude $H^+$ during the FP-induced acidosis in rat ventricular myocytes.

• The Korean Journal of Physiology
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• v.25 no.1
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• pp.49-60
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• 1991

The change of the acridine orange absorbance was used to monitor the formation and/or dissipation of a pH gradient in microvillous membrane vesicles (MVV) isolated from human term placenta. Under $Na^+$ efflux conditions, an acidification of the intravesicular space occured and it was completely inhibited by 0.1 mM amiloride. Under $K^+$ efflux conditions, an acidification of the intravesicular space occured and it was potentiated by valinomycin or FCCP. An inwardly directed chloride gradient also induced a minor intravesicular acidification, but it was not observed in voltage-clampled MVV. The initial rate of the dissipation of a pH gradient was accelerated by pulse injections of $Na^+$ in a saturable manner and $Li^+$ could replace $Na^+$. The kinetic parameter of $Na^+$ in placental $Na^+/H^+$ exchange was similar to that of renal $Na^+/H^+$ exchange. Amiloride was a inhibitor of directly coupled $Na^+/H^+$ exchange and its $IC_{50}$ in placental MVV was about 14-fold higher than that in renal brush border membrane. These results indicate that $Na^+/H^+$ exchanger exists in human placental MVV and that its kinetic characteristics is similar to that of renal $Na^+/H^+$ exchanger but its pharmacological characteristics is different. In placental MVV $K^+,\;H^+$, and, relatively minor chloride conductances are present. The magnitude of $Cl^-/OH^-$ exchange, even though it exists, seems to be smaller than that of $Na^+/H^+$ exchange.

• Animal cells and systems
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• v.13 no.3
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• pp.283-288
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• 2009

The ubiquitous plasma membrane $Na^+/H^+$ exchanger 1 (NHE1) is rapidly activated in response to various extracellular stimuli and maintains normal cytoplasmic pH. Yeast two-hybrid screening was used in order to identify proteins interacting with NHE1 using its cytoplasmic domain as a bait from HeLa cDNA library. One of the interacting cDNA clones was human Lactate dehydrogenase B (LDHB). In vitro translated LDHB was pulled down together with GST-NHE1.cd protein in the GST pull down assay, confirming the interaction in vitro. LDHB antibody immunoprecipitated endogenous LDHB together with NHE1 from H9c2 cells, validating cellular interaction between NHE1 and LDHB. Subsequent analysis revealed that the overexpression of LDHB increased intracellular PH, implying opening of the NHE1 transporter. Moreover, overexpression of LDHB activated caspase 3 and induced cell death, consistent with the expected phenotype of hyper-activation of NHE1. Collectively, our data indicate that LDHB modulates NHE1 activity via physical interaction.

• Polymer(Korea)
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• v.26 no.5
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• pp.661-669
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• 2002

The purpose of this research is to absorb and remove sulfur dioxide existing in the air by using ion exchange non-woven fabric. So we found out very appropriate condition of anionic exchange fabric scrubber by measuring amount of SO$_2$ adsorption under the atmosphere that concentration, velocity, and humidity was 100∼200 ppm, 0.6∼1.0 m/sec, and 30∼90 RH%, respectively. Ion exchange capacity of ion exchanger showed the maximum value, 3.75 meq/g at pH 4, and adsorption equilibrium time was the maximum value, 30 h when gas velocity was 0.6 m/sec, moreover, at 80$\^{C}$, adsorption equilibrium time tended to decrease more than 10 h. When concentration was 200 ppm, while reaction speed between SO$_2$ and ligand of fibrous ion exchanger was getting faster, adsorption break point had a tendency to get faster as well. In addition, when relative humidity in the scrubber was 90%, adsorption efficiency was 7.6%/h that seemed to be 30% higher than 4.6%/h coming from the condition that relative humidity had been 30%, and it was totally absorbed under 5 wt% NaOH solution in 5 minutes.

• Journal of the Korean Chemical Society
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• v.37 no.5
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• pp.491-495
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• 1993

Synthesis of polymer-supported azacrown ether ion exchanger, {(4,5): (13,14)-dibenzo-6,9,12-trioxa-3,15,21-triazazabicyclo[15.3.1]heneicosa-1(21),17,19-triene-2,16-dione : DBPDA ion exchanger}, and its ion binding ability to alkali metal $(Li^+,\;Na^+,\;K^+)$ picrates were studied. The binding constants $(K_b)$ of DBPDA ion exchanger to the alkali metal picrates in ether type solvents were obtained by spectrophotometry. Binding constants of alkali metal ions were in the order to Li < Na < K, and alkali metal ions were formed 1 : 1 complexes with ligands of DBPDA ion exchanger. Also, $K_b$ was found to depend on the variables such as solvent and temperature. The binding constants for the complexes were obtained in the ranges of $2{\times}10^3{\sim}4{\times}10^4M^{-1}$. In order to obtain the enthalpy (${\Delta}$H) and entropy changes (${\Delta}$S)n the complexation process, Kb were plotted against the temperature in the ranges of 10∼40$^{\circ}C$ according to the van't Hoff theory. Enthalphy and entropy changes were found in the ranges of -2.71∼-3.79 kcal/mol, and -16.52∼-20.57 eu, respectively.

• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.53-58
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• 2001

Sulfonated poly(phenylene sulfide) (SPPS) polymers were prepared by sulfonation of poly[methyl[4-(phenylthio) phenyl]sulfonium trifluoromethanesulfonate] (PPST) with fumic sulfonic acid (10% $SO_3-H_2SO_4$) and demethylation with aqueous NaOH solution. The equilibrium constants of ion exchange reactions between alkali metal cations ($Li^+,\;Na^+,\;and\;K^+$) and SPPS ion exchanger in organic solvents such as tetrahydrofuran (THF) and dioxane were measured. The equilibrium constants of ion exchange reactions increased as the polarity of the solvent increased, and the reaction temperature decreased. The equilibrium constants of the ion exchange reaction ($K_{eq}$) also increased in the order of $Li^+,\;Na^+,\;and\;K^+$. To elucidate the spontaneity of the exchange reaction in organic solvents, the enthalpy, entropy, and Gibbs free energy were calculated. The enthalpy of reaction ranged from -0.88 to -1.33 kcal/mol, entropy ranged from 1.42 to 4.41 cal/Kmol, and Gibbs free energy ranged from -1.03 to -2.55 kcal/mol. Therefore, the exchange reactions were spontaneous because the Gibbs free energies were negative. The SPPS ion exchanger and alkali metal ion bounding each other produced good ion exchange capability in organic solvents.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1169-1178
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• 1998

This study was performed to purify fig pectinesterase(F-PE) and characterize its in situ activity. Three kinds of F-PE were partially separated by using ammonium sulfate fractionation, Q-Sepharose column, CM-cation exchanger column chromatography, and HPLC. One of those was anionic protein and the others were cationic proteins. All of them had approximate molecular weight of 27,000 and lost rapidly their activity during storage. Therefore alternative crude enzyme was prepared by suspending the freeze dried and milled fig powder in 0.1 M NaCl at pH 7.5. F-PE had the optimum pH of 8.5, the optimum temperature of $50^{\circ}C$ with activation energy of 7,671 cal $mol^{-1}K^{-1}$ and stability up to $55^{\circ}C$ with 10 minutes heating. Optimum activity was obtained in $0.2{\sim}0.4$ M NaCl with optimum solubility at above 0.8 M NaCl.