Intracellular pH homeostasis in cultured human placental syncytiotrophoblast cells: recovery from acidification

2005 ◽  
Vol 288 (4) ◽  
pp. C891-C898 ◽  
Author(s):  
Elizabeth A. Cowley ◽  
Mary C. Sellers ◽  
Nicholas P. Illsley
Keyword(s):  
Intracellular Ph ◽  
Driving Force ◽  
Progressive Decrease ◽  
Ph Homeostasis ◽  
Ion Substitution ◽  
Recovery From Acidification ◽  
Acid Load ◽  
Acidification Recovery ◽  
Intracellular Acid

Resting or basal intracellular pH (pHi) measured in cultured human syncytiotrophoblast cells was 7.26 ± 0.04 (without HCO3−) or 7.24 ± 0.03 (with HCO3−). Ion substitution and inhibitor experiments were performed to determine whether common H+-transporting species were operating to maintain basal pHi. Removal of extracellular Na+ or Cl− or addition of amiloride or dihydro-4,4′-diisothiocyanatostilbene-2,2′-disulfonate (H2DIDS) had no effect. Acidification with the K+/H+ exchanger nigericin reduced pHi to 6.25 ± 0.15 (without HCO3−) or 6.53 ± 0.10 (with HCO3−). In the presence of extracellular Na+, recovery to basal pHi was prompt and occurred at similar rates in the absence and presence of HCO3−. Ion substitution and inhibition experiments were also used to identify the species mediating the return to basal pHi after acidification. Recovery was inhibited by removal of Na+ or addition of amiloride, whereas removal of Cl− and addition of H2DIDS were ineffective. Addition of the Na+/H+ exchanger monensin to cells that had returned to basal pHi elicited a further increase in pHi to 7.48 ± 0.07. Analysis of recovery data showed that there was a progressive decrease in ΔpH per minute as pHi approached the basal level, despite the continued presence of a driving force for H+ extrusion. These data show that in cultured syncytial cells, in the absence of perturbation, basal pHi is preserved despite the absence of active, mediated pH maintenance. They also demonstrate that an Na+/H+ antiporter acts to defend the cells against acidification and that it is the sole transporter necessary for recovery from an intracellular acid load.

Regulation of intracellular pH in J774 murine macrophage cells: H+ extrusion processes

1995 ◽  
Vol 268 (1) ◽  
pp. C210-C217 ◽  
Author(s):  
L. C. McKinney ◽  
A. Moran
Keyword(s):  
Intracellular Ph ◽  
Initial Rate ◽  
Adherent Cells ◽  
Murine Macrophage ◽  
Bafilomycin A1 ◽  
Macrophage Cell ◽  
Recovery From Acidification ◽  
J774 Cells ◽  
Acid Load ◽  
Rate Of Recovery

Mechanisms of intracellular pH (pHi) regulation were characterized in the murine macrophage cell line J774.1, using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein to measure pHi. Under nominally HCO3(-)-free conditions, resting pHi of nonadherent J774.1 cells was 7.53 +/- 0.02 (n = 86), and of adherent cells was 7.59 +/- 0.02 (n = 97). In the presence of HCO3-/CO2, pHi values were reduced to 7.41 +/- 0.02 (n = 12) and 7.40 +/- 0.01 (n = 28), respectively. Amiloride, an inhibitor of Na+/H+ exchange, did not affect resting pHi. Inhibitors of a vacuolar type H(+)-ATPase [bafilomycin A1, N-ethylmaleimide (NEM), 7-chloro-4-nitrobenz-2-oxa-1,3-diazide (NBD), and p-chloromercuriphenylsulfonic acid (pCMBS)] reduced pHi by at least 0.2 pH units. Inhibitors of other classes of H(+)-ATPases (oligomycin, azide, vanadate, and ouabain) were without effect. Inhibition of H+ efflux, measured by the change in extracellular pH of a weakly buffered cell suspension, followed the same pharmacological profile, indicating that the reduction of pHi was due to inhibition of H+ extrusion. Mechanisms of recovery from an imposed intracellular acid load were also investigated. In NaCl-Hanks' solution, pHi recovered exponentially to normal within 2 min. The initial rate of recovery was inhibited > 90% by amiloride or by replacement of extracellular Na+ concentration by N-methyl-glucamine. Inhibitors of the vacuolar H(+)-ATPase also inhibited recovery. NEM and NBD nonspecifically inhibited all recovery. Bafilomycin A1 and pCMBS did not inhibit the initial amiloride-sensitive portion of recovery, but they did inhibit a late component of recovery when pHi was above 7.0. We conclude that the Na+/H+ exchanger is primarily responsible for recovery from an acid load but does not regulate resting pHi. Conversely, a vacuolar H(+)-ATPase regulates the resting pHi of J774 cells but contributes little to recovery from acidification.

Intracellular pH regulation in the rabbit cortical collecting duct A-type intercalated cell

1997 ◽  
Vol 273 (3) ◽  
pp. F340-F347 ◽  
Author(s):  
A. E. Milton ◽  
I. D. Weiner
Keyword(s):  
Intracellular Ph ◽  
Ph Regulation ◽  
Collecting Duct ◽  
Cortical Collecting Duct ◽  
Bafilomycin A1 ◽  
Proton Secretion ◽  
Acid Load ◽  
A Cell ◽  
Phi Regulation ◽  
Intracellular Acid

The A cell may possess multiple H+ transporters, including H(+)-adenosinetriphosphatase (H(+)-ATPase) and H(+)-K(+)-ATPase. The current study examines the relative roles of proton transporters in the A cell by observing their contribution to both basal intracellular pH (pHi) regulation and pHi recovery from an intracellular acid load. CCD were studied using in vitro microperfusion, and pHi was measured in the individual A cell using the fluorescent, pH-sensitive dye, 2',7'-bis(carboxyethyl)-5(6)-carboxy-fluorescein (BCECF). Inhibiting H(+)-ATPase with luminal bafilomycin A1 decreased basal pHi, whereas inhibiting apical H(+)-K(+)-ATPase with either luminal Sch-28080 or luminal potassium removal did not. The predominant mechanism of pHi, recovery from an intracellular acid load was peritubular sodium dependent and peritubular ethylisopropylamiloride (EIPA) sensitive, identifying basolateral Na+/H+ exchange activity. In the absence of peritubular sodium, pHi recovery was inhibited by luminal bafilomycin A1 but not by luminal Sch-28080 addition or by luminal potassium removal. However, when Na+/H+ exchange was inhibited with EIPA, both bafilomycin A1 sensitive and potassium dependent, Sch-28080-sensitive components of pHi recovery were present. Quantitatively, the rate of H(+)-ATPase proton secretion was greater than the rate of H(+)-K(+)-ATPase proton secretion. We conclude that basolateral Na+/H+ exchange is the predominant mechanism of A cell pHi recovery from an intracellular acid load. An apical H(+)-ATPase is the primary apical transporter contributing to A cell pHi regulation. An apical H(+)-K(+)-ATPase, while present, plays a more limited role under the conditions tested.

HMG CoA reductase inhibitors affect Na(+)-H+ antiport activity in human lymphoblasts

1991 ◽  
Vol 261 (5) ◽  
pp. C780-C786 ◽  
Author(s):  
L. L. Ng ◽  
J. E. Davies
Keyword(s):  
Intracellular Ph ◽  
Inhibitory Effect ◽  
Hmg Coa Reductase ◽  
Reductase Inhibitors ◽  
Hmg Coa Reductase Inhibitors ◽  
Acid Load ◽  
Membrane Bound ◽  
Osmotic Stimulus ◽  
Coa Reductase ◽  
Intracellular Acid

The Na(+)-H+ antiport is a membrane-bound glycoprotein that extrudes intracellular acid loads and regulates cellular volume. Cellular synthesis of the oligosaccharide side chains of glycoproteins is dependent on a supply of mevalonate, itself a product of the rate-limiting enzyme of cholesterol synthesis 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase. The effect of two HMG CoA reductase inhibitors (simvastatin and 25-hydroxycholesterol) on intracellular pH and Na(+)-H+ exchange was therefore studied. Inhibition of the Na(+)-H+ antiport by these agents led to a fall in intracellular pH but did not impair the regulatory volume increase response to a hypertonic stimulus. The inhibitory effect of simvastatin was prevented by mevalonate but not dolichol or squalene. The effect of 25-hydroxycholesterol was more complex and not easily reversed. Thus HMG CoA reductase inhibitors reduced the ability of human lymphoblasts to expel an intracellular acid load via the Na(+)-H+ antiport, although the response of the antiport to an osmotic stimulus was preserved.

Influence of surface pH on intracellular pH regulation in cardiac and skeletal muscle

1986 ◽  
Vol 250 (5) ◽  
pp. C748-C760 ◽  
Author(s):  
B. Vanheel ◽  
A. de Hemptinne ◽  
I. Leusen
Keyword(s):  
Intracellular Ph ◽  
Soleus Muscle ◽  
Ph Regulation ◽  
Purkinje Fiber ◽  
Intracellular Acidification ◽  
Surface Ph ◽  
Acid Load ◽  
Rat Soleus Muscle ◽  
Rate Of Recovery ◽  
Intracellular Acid

The influence of the surface pH (pHs) on the intracellular pH (pHi) and the recovery of pHi after an imposed intracellular acid load was investigated in isolated sheep cardiac Purkinje fiber, rabbit papillary muscle, and mouse and rat soleus muscle. pHs and pHi, respectively, were continuously measured by use of single- and double-barreled pH-sensitive glass microelectrodes. Surface acidosis, usually obtained by superfusion with solutions of acid pH, was also produced with low buffered (5 mM N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid) solutions at control pH. The pHs decrease (delta pHs) induced by low buffering was smallest (-0.08 pH unit) in Purkinje fiber and largest (-0.31 pH unit) in rat soleus muscle, which already had a more acid surface in control conditions. delta pHs was somewhat dependent on the superfusion rate. Higher superfusion rates decreased but did not abolish delta pHs. Surface acidosis was associated with a small intracellular acidification. Intracellular acid loads were produced by adding and subsequently withdrawing 20 meq/l NH4+ from the superfusate. In all preparations, the rate of recovery of pHi after NH4+ withdrawal was notably decreased at acidified pHs. This effect was amiloride sensitive. It is concluded that, in superfused multi-cellular preparations, pHs and therefore the buffer concentration of a superfusate can considerably influence steady-state pHi and pHi recovery from an imposed intracellular acid load.

scholarly journals Intracellular pH regulation in cultured embryonic chick heart cells. Na(+)-dependent Cl-/HCO3- exchange.

1990 ◽  
Vol 96 (6) ◽  
pp. 1247-1269 ◽  
Author(s):  
S Liu ◽  
D Piwnica-Worms ◽  
M Lieberman
Keyword(s):  
Steady State ◽  
Intracellular Ph ◽  
Ph Regulation ◽  
Heart Cells ◽  
Efflux Rate Constant ◽  
Recovery From Acidification ◽  
Acid Load ◽  
Chick Heart ◽  
Embryonic Chick Heart ◽  
Phi Regulation

The contribution of Cl-/HCO3- exchange to intracellular pH (pHi) regulation in cultured chick heart cells was evaluated using ion-selective microelectrodes to monitor pHi, Na+ (aiNa), and Cl- (aiCl) activity. In (HCO3- + CO2)-buffered solution steady-state pHi was 7.12. Removing (HCO3- + CO2) buffer caused a SITS (0.1 mM)-sensitive alkalinization and countergradient increase in aiCl along with a transient DIDS-sensitive countergradient decrease in aiNa. SITS had no effect on the rate of pHi recovery from alkalinization. When (HCO3- + CO2) was reintroduced the cells rapidly acidified, aiNa increased, aiCl decreased, and pHi recovered. The decrease in aiCl and the pHi recovery were SITS sensitive. Cells exposed to 10 mM NH4Cl became transiently alkaline concomitant with an increase in aiCl and a decrease in aiNa. The intracellular acidification induced by NH4Cl removal was accompanied by a decrease in aiCl and an increase in aiNa that led to the recovery of pHi. In the presence of (HCO3- + CO2), addition of either amiloride (1 mM) or DIDS (1 mM) partially reduced pHi recovery, whereas application of amiloride plus DIDS completely inhibited the pHi recovery and the decrease in aiCl. Therefore, after an acid load pHi recovery is HCO3o- and Nao- dependent and DIDS sensitive (but not Ca2+o dependent). Furthermore, SITS inhibition of Na(+)-dependent Cl-/HCO3- exchange caused an increase in aiCl and a decrease in the 36Cl efflux rate constant and pHi. In (HCO3- + CO2)-free solution, amiloride completely blocked the pHi recovery from acidification that was induced by removal of NH4Cl. Thus, both Na+/H+ and Na(+)-dependent Cl-/HCO3- exchange are involved in pHi regulation from acidification. When the cells became alkaline upon removal of (HCO3- + CO2), a SITS-sensitive increase in pHi and aiCl was accompanied by a decrease of aiNa, suggesting that the HCO3- efflux, which can attenuate initial alkalinization, is via a Na(+)-dependent Cl-/HCO3- exchange. However, the mechanism involved in pHi regulation from alkalinization is yet to be established. In conclusion, in cultured chick heart cells the Na(+)-dependent Cl-/HCO3- exchange regulates pHi response to acidification and is involved in the steady-state maintenance of pHi.

Surface pH and the control of intracellular pH in cardiac and skeletal muscle

1987 ◽  
Vol 65 (5) ◽  
pp. 970-977 ◽  
Author(s):  
A. de Hemptinne ◽  
R. Marrannes ◽  
B. Vanheel
Keyword(s):  
Surface Layer ◽  
Intracellular Ph ◽  
Indirect Evidence ◽  
Weak Acid ◽  
Proton Extrusion ◽  
Surface Ph ◽  
Cat Papillary Muscle ◽  
Acid Load ◽  
Rat Soleus Muscle ◽  
Intracellular Acid

Both surface pH (pHs) and intracellular pH (pHi) were measured using single- and double-barreled pH-sensitive microelectrodes in isolated sheep cardiac Purkinje strands, rabbit and cat papillary muscle, and mouse and rat soleus muscle. Superfusion of the preparations with a relatively low buffered solution (containing 5 mM HEPES buffered to control pH) causes surface acidosis that correlates with efflux of metabolically produced acids in the unstirred layer of fluid surrounding the tissue. Acidification of the surface layer induces a slower acid change of pHi and depresses the rate of proton extrusion following an imposed intracellular acid load. In cardiac preparations, the lowering of pHi correlates with depression of twitch tension. Transient changes of pHs and pHi are seen when a weak acid or base is suddenly added to, or removed from the superfusion solution. Indirect evidence of the presence of carbonic anhydrase in the extracellular surface layer is obtained from analysis of transient pHs changes in presence and absence of acetazolamide.

Intracellular pH homeostasis during cell-cycle progression and growth state transition in Schizosaccharomyces pombe

2001 ◽  
Vol 114 (16) ◽  
pp. 2929-2941 ◽  
Author(s):  
Jim Karagiannis ◽  
Paul G. Young
Keyword(s):  
Cell Cycle ◽  
Schizosaccharomyces Pombe ◽  
Intracellular Ph ◽  
Cell Cycle Progression ◽  
State Transition ◽  
Homeostatic Regulation ◽  
Ph Homeostasis ◽  
Vegetative Cells ◽  
Growth State ◽  
Internal Ph

Accurate measurement of intracellular pH in unperturbed cells is fraught with difficulty. Nevertheless, using a variety of methods, intracellular pH oscillations have been reported to play a regulatory role in the control of the cell cycle in several eukaryotic systems. Here, we examine pH homeostasis in Schizosaccharomyces pombe using a non-perturbing ratiometric pH sensitive GFP reporter. This method allows for accurate intracellular pH measurements in living, entirely undisturbed, logarithmically growing cells. In addition, the use of a flow cell allows internal pH to be monitored in real time during nutritional, or growth state transition. We can find no evidence for cell-cycle-related changes in intracellular pH. By contrast, all data are consistent with a very tight homeostatic regulation of intracellular pH near 7.3 at all points in the cell cycle. Interestingly, pH set point changes are associated with growth state. Spores, as well as vegetative cells starved of either nitrogen, or a carbon source, show a marked reduction in their internal pH compared with logarithmically growing vegetative cells. However, in both cases, homeostatic regulation is maintained.

Intracellular pH transients in rat diaphragm muscle measured with DMO

1978 ◽  
Vol 235 (1) ◽  
pp. C49-C54 ◽  
Author(s):  
A. Roos ◽  
W. F. Boron
Keyword(s):  
Intracellular Ph ◽  
Weak Acid ◽  
Diaphragm Muscle ◽  
Disulfonic Acid ◽  
Free Solution ◽  
Rat Diaphragm ◽  
Control Value ◽  
Acid Load ◽  
Acid Extrusion ◽  
Acid Loading

Changes of the intracellular pH of rat diaphragm muscle were monitored at 30-min intervals with the weak acid DMO (5,5-dimethyl-2,4-oxazolidinedione). Transferring the muscle from a CO2-containing to a CO2-free solution caused intracellular pH (pHi) to rise by an average of 0.18 during the first 30 min and then to level off at a slightly lower value over the next 60-90 min. Transferring the muscle from a CO2-free to a CO2-containing solution caused pHi to fall by 0.18 during the first 30 min and then to recover by 0.05 over the next 90 min. Subsequent return to the CO2-free solution caused pHi to overshoot the control value by 0.10. Both the recovery and the overshoot can be accounted for by an acid-extruding pump. Intracellular acid loading with 118 mM DMO similarly caused pHi to fall initially, to recover slowly during the acid loading, and then to overshoot the control pHi on removal of the acid load. In the absence of HCO3-/CO2, acid extrusion was reduced by about a fifth. SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid) had no effect. The absence of either Na+ or Cl- from HCO3-/CO2- free solution reduced acid extrusion by about a half.

pH regulation in ileum: Na(+)-H+ and Cl(-)-HCO3- exchange in isolated crypt and villus cells

1991 ◽  
Vol 260 (3) ◽  
pp. G440-G449 ◽  
Author(s):  
U. Sundaram ◽  
R. G. Knickelbein ◽  
J. W. Dobbins
Keyword(s):  
Intracellular Ph ◽  
Ph Regulation ◽  
Second Messengers ◽  
Cell Types ◽  
Current Evidence ◽  
Leucine Incorporation ◽  
Trypan Blue Exclusion ◽  
Morphological Criteria ◽  
Acid Load ◽  
Separation Cell

Current evidence suggests that intestinal crypt and villus cells have different functions in electrolyte transport. To study the regulation of transporters, we isolated and separated these two cell types. This was accomplished by sequential collection of enterocytes from rabbit ileal loops incubated with buffered solutions of calcium chelators. Alkaline phosphatase and thymidine kinase activity, sodium-glucose cotransport, and morphological criteria were used to determine cell separation. Cell viability was evaluated with trypan blue exclusion, leucine incorporation into protein, and morphological features. The role of Na(+)-H+ and Cl(-)-HCO3- exchange in the regulation of intracellular pH was analyzed using an intracellular pH sensitive dye, BCECF. Removal of external Na+ or the addition of amiloride resulted in acidification of both crypt and villus cells. Removal of Cl- or the addition of DIDS resulted in alkalinization of both cell types. The cells could be acidified with NH4Cl, and recovery from this acid load was dependent on Na+ and inhibited by amiloride. Similarly, the cells could be alkalinized with propionate and recovery was Cl- dependent and DIDS sensitive. These data are consistent with the presence of Na(+)-H+ and Cl(-)-HCO3- exchange in both crypt and villus cells. Both exchanges appear to be involved in the regulation of basal pH as well as in recovery from alterations in intracellular pH. Having demonstrated the presence of Na(+)-H+ and Cl(-)-HCO3- exchange activity in both crypt and villus cells, we can now use these cells to determine the regulation of these exchangers by intracellular second messengers.

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