Kinetics of the Na+-H+ antiporter as assessed by the change in intracellular pH in MDCK cells

1986 ◽  
Vol 251 (4) ◽  
pp. C558-C562 ◽  
Author(s):  
A. M. Selvaggio ◽  
J. H. Schwartz ◽  
H. H. Bengele ◽  
E. A. Alexander
Keyword(s):  
Intracellular Ph ◽  
Mdck Cells ◽  
Choline Chloride ◽  
Maximum Velocity ◽  
Ph Sensitive ◽  
Proton Efflux ◽  
Saturation Kinetics ◽  
Free Choline ◽  
Kinetics Of ◽  
Phi Regulation

The Na+-H+ antiporter regulates both H+ secretion and cell pH in renal epithelia. The present study was designed to further define the Na+ dependency and kinetics of proton efflux in MDCK cells. Intracellular pH (pHi) was determined with a pH-sensitive fluorescent probe, 2,7-bis-carboxyethyl-5,6-carboxyfluorescein (BCECF). Data were obtained from confluent monolayers grown on plastic cover slips and studied in media free of added CO2 and HCO-3, pH = 7.2 (pHo). Monolayers in NaCl maintain a pHi of 7.48 +/- 0.03 (n = 13). When cells were acidified with NH4Cl, pHi decreased to 6.73 +/- 0.07 (n = 10) and remained stable in Na+-free choline chloride. When monolayers were subsequently exposed to NaCl, pHi increased 0.28 +/- 0.04 pH units/min. Amiloride (2.5 mM) inhibited this Na+-dependent rise in pHi by more than 75%. The rate of pHi recovery after exposure to Na+ exhibited saturation kinetics; the apparent Km(Na) was 30.4 +/- 4.2 mM and maximum velocity was 107.1 +/- 17.1 delta [H+]i nmol X l-1 X min-1. We conclude that pHi regulation in the MDCK cell is in part mediated by a Na+-H+ antiporter, and the kinetics of this process can be reliably assessed by the pH-sensitive fluorometric probe, BCECF.

Modulation of Na-H antiporter activity in human lymphoblasts by altered membrane cholesterol

1991 ◽  
Vol 261 (6) ◽  
pp. C1138-C1142 ◽  
Author(s):  
C. E. Poli de Figueiredo ◽  
L. L. Ng ◽  
J. E. Davis ◽  
F. J. Lucio-Cazana ◽  
J. C. Ellory ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Maximum Velocity ◽  
Ph Sensitive ◽  
Membrane Cholesterol ◽  
Cholesterol Depletion ◽  
Proton Efflux ◽  
Efflux Rate ◽  
In Situ Modification

The effects of changes in membrane cholesterol on Na-H antiporter activity in culture human lymphoblasts are described. Lymphoblast cholesterol alteration was achieved with liposomes of phosphatidylcholine (cholesterol depletion) or phosphatidylcholine plus cholesterol (cholesterol enrichment). Lymphoblast intracellular pH (pHi) was examined by fluorimetry using cells loaded with the pH-sensitive dye 2',7'-bis(2-carboxyethyl)5(6)-carboxyfluorescein, and the Na-dependent proton efflux rate at a pHi of 6.0 was taken as the maximum velocity of the Na-H antiporter. Lymphoblast membrane cholesterol depletion activated the Na-H antiporter, and enrichment of membrane cholesterol caused inhibition of the antiporter activity. This study demonstrates that in situ modification of membrane cholesterol can modulate the activity of the Na-H antiporter.

Basis for apparent saturation kinetics of Na+ influx in freshwater hyperregulators

1988 ◽  
Vol 254 (6) ◽  
pp. R984-R988
Author(s):  
L. B. Kirschner
Keyword(s):  
Transport System ◽  
Open Circuit ◽  
Na Transport ◽  
Proton Efflux ◽  
Electrical Neutrality ◽  
Saturation Kinetics ◽  
Kinetics Of ◽  
Stimulation Of ◽  
Cl Permeability

Uptake of Na+ by intact frogs has been reported to show saturation kinetics at low external concentrations (less than 2 mM); yet other evidence shows that the transport system is far from saturated in this concentration range. The saturation behavior was reproduced here in isolated frog skins that were then used as appropriate models for investigating the paradox. When the skin was bathed by 2 mM Na+ outside and open circuited, influx (JNain) was near maximum. If, under these conditions, the skin was short circuited, JNain increased threefold. Alternatively, if Cl- permeability was increased in the open-circuited skin, JNain doubled. Both perturbations uncouple JNain from the efflux of a cation (nominally H+), which normally maintains electrical neutrality under open-circuit conditions. This suggests that the apparent saturation of JNain is caused by limiting efflux of the counterion. In confirmation of this prediction, stimulation of proton efflux markedly increased JNain. Thus the apparent Michaelis-Menten kinetics observed in frogs, and probably in other freshwater animals as well, do not represent saturation of an element in Na+ transport, either the amiloride-sensitive apical channel or the basolateral Na+-K+-ATPase.

Influence of endothelial volume on kinetics of reacting indicators in the lung

1984 ◽  
Vol 57 (5) ◽  
pp. 1528-1530 ◽  
Author(s):  
T. R. Harris
Keyword(s):  
Lung Injury ◽  
Enzyme Kinetics ◽  
Bolus Injection ◽  
Maximum Velocity ◽  
Capillary Surface ◽  
Saturation Kinetics ◽  
Multiple Indicator ◽  
The Relationship ◽  
Kinetics Of ◽  
Enzyme Characteristic

The purpose of this work is to show mathematically the relationship between the classical maximum velocity of reaction, Vmax, for enzyme kinetics and an analogous parameter, Vmax, derived by Linehan and Dawson (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 47:404–411, 1979) for the analysis of tracers which disappear by saturation kinetics from the lung circulation during the passage of indicators after bolus injection. Rederivation of the original equation for the combination of flow and reaction in a capillary showed that Vmax is equal to the product of enzyme Vmax and the volume of endothelium, Ve, in which the enzyme resides. This implies that Vmax interpreted from multiple-indicator curves in the lung by the Linehan-Dawson method is a combination of an enzyme characteristic Vmax and a measure of functioning capillary surface during passage, Ve. Lung injury could change Vmax, functioning surface (Ve), or both.

scholarly journals Na+ modulates carrier-mediated Fe2+ transport through the erythroid cell membrane

1991 ◽  
Vol 275 (3) ◽  
pp. 635-638 ◽  
Author(s):  
A Egyed
Keyword(s):  
Cell Membrane ◽  
Choline Chloride ◽  
Maximum Velocity ◽  
Erythroid Cell ◽  
Exchange System ◽  
Ph Optimum ◽  
Low Concentrations ◽  
Free Choline ◽  
Uptake Process ◽  
Rabbit Reticulocytes

The effects of univalent cations on Fe2+ uptake by rabbit reticulocytes have been studied. The rate of Fe2+ uptake was almost identical when measured in Na(+)-free choline chloride or KCl medium. Na+ but not Li+ inhibited Fe2+ uptake even at relatively low concentrations (2.5-20 mM) in these media. In contrast to this effect of extracellular Na+, the rate of Fe2+ uptake was facilitated by an increase in the intracellular Na2+ concentration in the range 5-40 mM, suggesting that intracellular Na+ is required for the uptake process. This effect also appears to be specific for Na+. Amiloride inhibited Fe2+ uptake in KCl (or in choline chloride), but had little if any effect in NaCl. Therefore a Na(+)- and amiloride-sensitive and a Na(+)- and amiloride-insensitive component can be distinguished. The two components differ in maximum velocity and pH optimum, but not in their apparent affinity for Fe2+. The ineffectiveness of selective inhibitors excludes the involvement of the Na+/H+ or Na+/Ca2+ exchange mechanisms. To account for the results presented in this work, a Na+/Fe2+ exchange system in the erythroid cell membrane is proposed.

scholarly journals Gelatin Beads/Hemp Hurd as pH Sensitive Devices for Delivery of Eugenol as Green Pesticide

2021 ◽  
Author(s):  
Gianluca Viscusi ◽  
Giuliana Gorrasi
Keyword(s):  
Release Kinetics ◽  
Barrier Properties ◽  
Ph Sensitive ◽  
Release Behavior ◽  
Sorption Coefficient ◽  
Highly Sensitive ◽  
Mean Diameter ◽  
Ph Conditions ◽  
Kinetics Of ◽  
Hemp Hurd

AbstractIn this paper gelatin beads reinforced with natural hemp hurd have been produced as pH sensitive devices for the release of eugenol, as green pesticide. The composites beads, with a mean diameter of about 1 mm, were obtained by polymer droplet gelation in sunflower oil. Thermal properties were evaluated showing no noticeable difference after the introduction of hemp hurd. Barrier properties demonstrated an improvement of hydrophobization. The introduction of 5% w/w of hemp hurd led to a reduction of sorption coefficient of about 85% compared to unloaded gelatin beads. Besides, the diffusion coefficient decreased, introducing 5% w/w of hemp hurd, from 8.91 × 10−7 to 0.77 × 10−7 cm2/s. Swelling and dissolution phenomena of gelatin beads were studied as function of pH. The swelling of gelatin beads raised as pH increased up to 2.3 g/g, 9.1 g/g and 27.33 g/g at pH 3, 7 and 12, respectively. The dissolution rate changed from 0.034 at pH 3 to 0.077 h−1 at pH 12. Release kinetics of eugenol at different pH conditions were studied. The released eugenol after 24 h is 98%, 91%, 81 and 63% w/w (pH 3), 87%, 62%, 37 and 32 wt% (pH 7) and 81%, 68%, 60 and 52 wt% (pH 12) for unloaded gelatin beads and gelatin beads with 1%, 3 and 5% of hemp hurd, respectively. The eugenol release behavior was demonstrated to be highly sensitive to the pH release medium, which allows to tune such devices as green pesticide release systems in soils with different level of acidity/basicity.

LONG TERM EFFECTS OF THYROID STIMULATING HORMONE AND INSULIN ON INTRACELLULAR pH IN FRTL-5 CELLS

1992 ◽  
Vol 133 (2) ◽  
pp. R9-R11
Author(s):  
A.M. Wood ◽  
S.P. Bidey ◽  
J. Soden ◽  
W.R. Robertson
Keyword(s):  
Intracellular Ph ◽  
Small Groups ◽  
Thyroid Stimulating Hormone ◽  
Ph Sensitive ◽  
Long Term Effects ◽  
Bicarbonate Ions ◽  
Chronic Effects ◽  
Petri Dishes ◽  
Presence And Absence

ABSTRACT We have studied the chronic effects of TSH (100μU/ml) and insulin (10μg/ml) on intracellular pH (pHi) in FRTL-5 cells using the pH sensitive probe 2′7-bis (2-carboxyethyl-5′-6′) carboxyfluorescein. FRTL-5 cells were cultured on Petri dishes either in the presence of 4H, ie. Coons F-12 containing cortisol (10nM), transferrin (0.5μg/ml), glycyl-histidyl lysine acetate (10ng/ml) and somatostatin (10μg/ml), or with 4H+insulin (5H), 4H+TSH, or 4H+TSH+insulin (6H). pHi was measured in small groups of cells by microspectrofluorimetry both in the presence and absence of bicarbonate ions after cells had been deprived of serum for at least a day. In

Intracellular pH-Sensitive PEG-block-Acetalated-Dextrans as Efficient Drug Delivery Platforms

2013 ◽  
Vol 5 (21) ◽  
pp. 10760-10766 ◽  
Author(s):  
Zhe Zhang ◽  
Xiaofei Chen ◽  
Li Chen ◽  
Shuangjiang Yu ◽  
Yue Cao ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Intracellular Ph ◽  
Ph Sensitive

Design and validation of a new ratiometric intracellular pH imaging probe using lanthanide-doped upconverting nanoparticles

2017 ◽  
Vol 46 (40) ◽  
pp. 13957-13965 ◽  
Author(s):  
Shuoren Du ◽  
Javier Hernández-Gil ◽  
Hao Dong ◽  
Xiaoyu Zheng ◽  
Guangming Lyu ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Quantitative Imaging ◽  
Living Cells ◽  
Ph Sensitive ◽  
Upconversion Nanoparticles ◽  
Imaging Probe ◽  
Ph Imaging ◽  
Ratiometric Probe ◽  
Subcellular Level

A ratiometric probe based on upconversion nanoparticles modified with a pH sensitive moiety for the quantitative imaging of pH at the subcellular level in living cells.

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