scholarly journals Relationship between intracellular proton buffering capacity and intracellular pH

1992 ◽  
Vol 41 (1) ◽  
pp. 43-49 ◽  
Author(s):  
David J.A. Goldsmith ◽  
Philip J. Hilton
Keyword(s):  
Intracellular Ph ◽  
Buffering Capacity ◽  
Proton Buffering

Exercise alters the regulation of myocardial Na+/H+ exchanger-1 activity

2013 ◽  
Vol 305 (10) ◽  
pp. R1182-R1189 ◽  
Author(s):  
Bryan J. Feger ◽  
Joseph W. Starnes
Keyword(s):  
Intracellular Ph ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Weight Ratio ◽  
Buffering Capacity ◽  
Strenuous Exercise ◽  
Sprague Dawley ◽  
Ph Buffering ◽  
Nhe1 Activity ◽  
Ph Buffering Capacity

The myocardial Na+/H+ exchanger-1 (NHE1) plays a major role in regulation of intracellular pH, and its upregulation has been implicated in increased ischemia-reperfusion injury and other pathologies. Hydrogen peroxide (H2O2) increases NHE1 activity acutely via ERK1/2 signaling. Chronic strenuous exercise upregulates NHE1 in skeletal muscle, but we hypothesize this will not occur in the heart, because exercise creates a cardioprotective phenotype. NHE1 activity and its regulation by H2O2 were examined at physiological pH using isolated cardiomyocytes from female Sprague-Dawley rats exercised on a treadmill for 5 wk (E; n = 11). Compared with sedentary (S; n = 15), E displayed increases ( P < 0.05) in heart-to-body weight ratio (6.8%) and plantaris mitochondria content (89%). NHE1 activity (acid efflux rate following an acid load) was 209% greater in E (0.65 ± 0.12 vs. 2.01 ± 0.29 fmol/min). The difference was attributed primarily to greater cell volume (22.2 ± 0.6 vs. 34.3 ± 1.1 pl) and intracellular pH-buffering capacity (33.94 ± 1.59 vs. 65.82 ± 5.20 mM/pH unit) of E myocytes. H2O2 stimulation (100 μM) raised NHE1 activity significantly less in E (45%) than S (167%); however, activity remained 185% greater in E. ERK1/2 inhibition abrogated the increases. H2O2-stimulated ERK1/2 phosphorylation levels normalized to total ERK1/2 were similar between groups. Content of NHE1 and activities of H2O2 scavengers were also similar. We observed that intracellular pH-buffering capacity differences between groups became progressively less with declining pH, which may be an exercise-induced cardioprotective adaptation to lower NHE1 activity during certain pathological situations. We conclude that strenuous endurance exercise increases myocardial NHE1 activity at physiological pH, which would likely enhance cardiac performance under physiological conditions.

Intracellular pH in the OK cell. I. Identification of H+ conductance and observations on buffering capacity

1991 ◽  
Vol 261 (6) ◽  
pp. C1143-C1153 ◽  
Author(s):  
M. Graber ◽  
J. DiPaola ◽  
F. L. Hsiang ◽  
C. Barry ◽  
E. Pastoriza
Keyword(s):  
Steady State ◽  
Intracellular Ph ◽  
Large Cell ◽  
Buffering Capacity ◽  
Disulfonic Acid ◽  
Transport Pathways ◽  
Opossum Kidney ◽  
Direct Titration ◽  
Cell Ph

The regulation of intracellular pH (pHi) in the opossum kidney (OK) cell line was studied in vitro using the pH-sensitive excitation ratio of 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Recovery from an NH4Cl acid load disclosed a Na-dependent component blocked by amiloride and a smaller Na-independent component. The Na-independent recovery rate was proportional to the H+ gradient from cell to buffer and was zero in the absence of an electrochemical gradient. The Na-independent recovery was not affected by N-ethylmaleimide, dicyclohexylcarbodiimide, HCO3, phloretin, or ZnCl2 but was accelerated in depolarized cells and by membrane-fluidizing drugs and was inhibited by glutaraldehyde. The apparent cellular buffering capacity changed in proportion to this H+ conductance. Consistent with an electrogenic H+ leak, steady-state cell pH alkalinized with depolarization and acidified with hyperpolarization. Removal of buffer Na+ produced a profound acidification, as did amiloride. In 0-Na+ buffers, extremely large cell-to-buffer H+ gradients were present and proportional to buffer pH. 4-Acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid had no effect on steady-state pHi. Measurements of intracellular buffering capacity were derived from the change of cell pH induced by withdrawing NH4Cl. This buffering capacity was increased threefold in Na-free buffers, whereas the value measured by direct titration of cell lysate was the same or less than that of control cells. The NH4Cl-derived buffering capacity varied in direct proportion to the magnitude of the H+ leak. Drugs that changed H+ permeability produced the apparent changes of the measured buffering capacity within a few minutes. We conclude that, in HCO3-free buffer, the OK cell uses two membrane acid-base transport pathways: a Na-H antiporter active at physiological pH and a substantial passive H+ conductance. The results also reveal that the NH4Cl-derived buffering capacity is subject to artifacts, possibly due to a finite leak of ionic NH4+.

Regulation of intracellular pH in crypt cells from rabbit distal colon

1994 ◽  
Vol 267 (3) ◽  
pp. G409-G415 ◽  
Author(s):  
S. L. Abrahamse ◽  
A. Vis ◽  
R. J. Bindels ◽  
C. H. van Os
Keyword(s):  
Intracellular Ph ◽  
Distal Colon ◽  
Buffering Capacity ◽  
Colonic Crypt ◽  
Bafilomycin A1 ◽  
Acid Load ◽  
Intracellular Buffering Capacity ◽  
Crypt Cells ◽  
Exchange Activity ◽  
In Cells

H+ secretory mechanisms and intrinsic intracellular buffering capacity were studied in crypt cells from rabbit distal colon. To this end crypts of Lieberkuhn were isolated by microdissection, and intracellular pH (pHi) was measured using digital imaging fluorescence microscopy and the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein. In the absence of HCO(3-)-CO2 and presence of Na+, resting pHi was 7.51 +/- 0.04 (n = 237/23, cells/crypts). However, 6 min after superfusion with a solution containing zero Na+, 1 x 10(5) M Sch-28080 and 5 x 10(-8) M bafilomycin A1, pHi in cells at the bottom of the crypts was significantly reduced, whereas pHi in cells at the top of the crypts remained unchanged. The intrinsic buffering capacity of cells from the middle to the top portion of crypts was significantly higher in the pHi range 7.2-7.6 than of cells at the bottom of the crypt. H+ secretion after an NH(4+)-NH3 pulse amounted to 245 +/- 53 microM/s (n = 73/7) at pHi 7.1 and was largely Na+ dependent and ethylisopropylamiloride sensitive. The Na(+)-independent recovery of pHi after an acid load was insensitive to Sch-28080 and bafilomycin A1. In conclusion, pHi in colonic crypt cells is regulated through Na+/H+ exchange activity in the absence of HCO3-. In addition, intracellular buffering capacity varied with the position along the crypt axis, whereas Na+/H+ exchange activity and pHi did not.

Initial effect of sodium bicarbonate on intracellular pH depends on the extracellular nonbicarbonate buffering capacity

2001 ◽  
Vol 29 (5) ◽  
pp. 1033-1039 ◽  
Author(s):  
Jacques Levraut ◽  
Carine Giunti ◽  
Jean-Pierre Ciebiera ◽  
Georges de Sousa ◽  
Roger Ramhani ◽  
...  
Keyword(s):  
Sodium Bicarbonate ◽  
Intracellular Ph ◽  
Buffering Capacity ◽  
Initial Effect

scholarly journals Impaired Na(+)-H+ exchanger activity of hepatocytes in chronic renal failure.

1997 ◽  
Vol 8 (6) ◽  
pp. 929-934
Author(s):  
M Michnowska ◽  
M Smogorzewski ◽  
S G Massry
Keyword(s):  
Renal Failure ◽  
Chronic Renal Failure ◽  
Secondary Hyperparathyroidism ◽  
Intracellular Ph ◽  
Cytosolic Calcium ◽  
Cation Transport ◽  
Buffering Capacity ◽  
The State ◽  
Kinetics Of ◽  
Reduced Activity

Available data indicate that cation transport is impaired in many cells in chronic renal failure (CRF). The information on the activity of the Na(+)-H+ exchanger in CRF is variable, and both increased and reduced activity have been reported. The mechanisms through which CRF may exert an effect on the Na(+)-H+ transport are not known. Data exist indicating that PTH inhibits the Na(+)-H+ exchange in kidney and liver, and this action of hormone is most likely due to its ability to raise cytosolic calcium ([Ca2+]i). Therefore, it is possible that excess PTH in CRF may adversely affect the activity of the Na(+)-H+ antiport. This study examines the activity of Na(+)-H+ antiport, intracellular pH (pHi), and buffering capacity of hepatocytes obtained from rats after 6 wk of CRF, from CRF parathyroidectomized animals, and from CRF rats and normal rats treated with verapamil. The pHi and the buffering capacity of hepatocytes were not different in all groups of animals. The activity of the Na(+)-H+ antiport of hepatocytes from CRF animals was significantly (P < 0.01) lower than in hepatocytes from normal rats, CRF parathyroidectomized rats, CRF rats treated with verapamil, and normal rats treated with verapamil, and the values in the latter four groups of animals were not different. This impaired activity of Na(+)-H+ antiport in CRF was observed in all external concentrations of sodium (25, 50, 75, 100, 125, and 150 mM). Thus, CRF altered the kinetics of the transporter in that its Vmax decreased and its K(m) increased. The data show that: (1) CRF is associated with reduction in the activity of Na(+)-H+ antiport in hepatocytes; (2) this defect is due to the state of secondary hyperparathyroidism of CRF; and (3) excess PTH mediates its effect by elevating [Ca2+]i of hepatocytes because treatment of CRF animals with verapamil, which blocks the PTH-induced rise in [Ca2+]i of these cells, prevented the impairment in the activity of the Na(+)-H+ antiport.

Na+/H+ antiport and buffering capacity in human polymorphonuclear and mononuclear leucocytes

1991 ◽  
Vol 80 (2) ◽  
pp. 95-99 ◽  
Author(s):  
V. Frighi ◽  
L. L. Ng ◽  
A. Lewis ◽  
H. Dhar
Keyword(s):  
Intracellular Ph ◽  
Mononuclear Cells ◽  
Cell Types ◽  
Buffering Capacity ◽  
Polymorphonuclear Cells ◽  
Polymorphonuclear Leucocytes ◽  
Significant Difference ◽  
Mononuclear Leucocytes

1. Na+/H+ antiport activity was measured in peripheral blood polymorphonuclear and mononuclear cells of 12 healthy subjects by using an intracellular pH clamp technique to determine the external Na+-dependent H+ efflux rate in cells loaded with a pH-sensitive fluorescent dye, bis(carboxyethyl)carboxyfluorescein. The change in external Na+ concentrations for all pH measurements was similar in both cell types. 2. A significant difference between the two types of cells was found, the polymorphonuclear leucocytes having a higher Na+/H+ antiport activity than the lymphocytes. Cellular intrinsic buffering capacity measured in the absence of HCO−3 was also higher in the polymorphonuclear cells than in the lymphocytes. 3. These differences may be associated with a difference in the role of the Na+/H+ exchanger in these two types of cells, although in vivo the presence of HCO−3/Cl− exchangers may also contribute to intracellular pH homoeostasis.

Sign in / Sign up

Export Citation Format

Share Document