Regulation of intracellular pH in the perfused heart by external HCO3- and Na(+)-H+ exchange

1993 ◽  
Vol 265 (1) ◽  
pp. H289-H298 ◽  
Author(s):  
A. A. Grace ◽  
H. L. Kirschenlohr ◽  
J. C. Metcalfe ◽  
G. A. Smith ◽  
P. L. Weissberg ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Cardiac Tissue ◽  
Intracellular Acidosis ◽  
Proton Efflux ◽  
Efflux Rate ◽  
Perfused Heart ◽  
Acid Load ◽  
Ethanesulfonic Acid ◽  
Intracellular Buffering Capacity ◽  
Ferret Heart

Both Na(+)-dependent HCO3- influx and the Na(+)-H+ antiport have been shown to contribute to recovery from intracellular acidosis in avian and mammalian cardiac tissue. We have investigated the participation of these mechanisms in the recovery of intracellular pH (pHi) after an acid load in the Langendorff-perfused ferret heart. pHi was measured from the phosphorus-31 nuclear magnetic resonance chemical shift of 2-deoxy-D-glucose 6-phosphate. Basal pHi was higher in HCO(3-)-buffered solution (7.05 +/- 0.01; n = 8) than in nominally HCO(3-)-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) solution (6.98 +/- 0.02; n = 9). Addition of 5-(N-ethyl-N-isopropyl)amiloride (EIPA) caused a significant fall in pHi in HEPES solution (6.91 +/- 0.02; n = 5) but not in HCO3- solution (7.02 +/- 0.02; n = 5). Intrinsic intracellular buffering capacity in 0 Na(+)-HEPES solution was 37 +/- 2 mmol/l (n = 4), and additional buffering due to HCO(3-)-CO2 was approximately 13 mmol/l in HCO3- solution. After an intracellular acidosis induced by an NH4Cl prepulse, the proton efflux rate (JH) at pHi 6.90 was 0.5 +/- 0.2 nmol.l-1.min-1 (n = 14) in HEPES solution and 1.2 +/- 0.4 mmol.l-1.min-1 (n = 13) in HCO3- solution. The addition of 1 microM EIPA effectively blocked proton efflux in HEPES solution (JH < 0.1 mmol.l-1.min-1; n = 8), whereas it slowed pHi recovery in HCO3- solution (JH = 0.6 +/- 0.2 mmol.l-1.min-1; n = 9). There was no recovery of pHi in Na(+)-free HCO3- solution (JH < 0.1 mmol.l-1.min-1; n = 3). The Na(+)-H+ antiport and a mechanism requiring both external Na+ and HCO3- each contribute approximately 50% to proton efflux at pHi 6.90 during the recovery from intracellular acidosis in the isolated perfused mammalian heart.

Intracellular pH recovery during respiratory acidosis in perfused hearts

1994 ◽  
Vol 266 (2) ◽  
pp. C489-C497 ◽  
Author(s):  
J. I. Vandenberg ◽  
J. C. Metcalfe ◽  
A. A. Grace
Keyword(s):  
Intracellular Ph ◽  
Cardiac Tissue ◽  
Respiratory Acidosis ◽  
Ph Indicator ◽  
Ethanesulfonic Acid ◽  
Intracellular Buffering Capacity ◽  
Acid Extrusion ◽  
Acid Loading ◽  
Perfused Hearts ◽  
Ferret Heart

Na(+)-H+ exchange and Na(+)-dependent HCO3- influx both contribute to recovery of intracellular pH (pHi) after an acidosis induced by using the NH4Cl prepulse technique in mammalian and avian cardiac tissue. We have investigated the relative contributions of these mechanisms to pHi recovery during respiratory acidosis in the Langendorff-perfused ferret heart with and without correction of extracellular pH (pHo). pHi was measured from the chemical shift of the exogenous 31P nuclear magnetic resonance pH indicator 2-deoxy-D-glucose 6-phosphate. Intrinsic intracellular buffering capacity, calculated from the change in intracellular HCO3- concentration after a change in CO2, was reduced from approximately 33 (no inhibitors of acid extrusion present) to 19 +/- 5 mM when H+ extrusion during the acid loading phase was inhibited. During respiratory acidosis (pHo approximately 6.95), the proton efflux rate (JH) calculated at pHi 6.85 was 0.30 +/- 0.04 mmol.l-1.min-1 (n = 9). When pHo was corrected by increasing external HCO3- concentration to 60 mM during respiratory acidosis (pHo approximately 7.33), JH was 1.11 +/- 0.11 mmol.l-1.min-1 (n = 7), and when pHo was partially corrected by the addition of 50 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid to the perfusion solution (pHo approximately 7.1), JH was 0.64 +/- 0.08 mmol.l-1.min-1 (n = 6). In all three groups Na(+)-H+ exchange and HCO3- influx each contributed approximately 50% to acid-equivalent efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II stimulates sodium-dependent proton extrusion in perfused ferret heart

1996 ◽  
Vol 270 (6) ◽  
pp. C1687-C1694 ◽  
Author(s):  
A. A. Grace ◽  
J. C. Metcalfe ◽  
P. L. Weissberg ◽  
H. W. Bethell ◽  
J. I. Vandenberg
Keyword(s):  
Angiotensin Ii ◽  
Cardiac Tissue ◽  
At1 Receptor ◽  
Intracellular Acidosis ◽  
Physiological Homeostasis ◽  
Cellular Dysfunction ◽  
Acid Loading ◽  
Contractile Recovery ◽  
Ferret Heart ◽  
Stimulation Of

The Na+/H+ antiport and Na(+)-HCO3- coinflux carrier contribute to recovery from intracellular acidosis in cardiac tissue. The effects of angiotensin II (10(-12)-10(-6) M) on H+ fluxes after intracellular acid loading and during reperfusion after myocardial ischemia have been investigated in the isovolumic, Langendorff-perfused ferret heart. Intracellular pH (pHi) was estimated using 31P nuclear magnetic resonance (NMR) spectroscopy from the chemical shift of intracellular deoxyglucose-6-phosphate or inorganic phosphate. Angiotensin II produced concentration-dependent stimulation (maximum at 10(-6) M: 67%) of 5-(N-ethyl-N-isopropyl)amiloride (EIPA)-sensitive Na(+)-dependent of H+ efflux consistent with stimulation of the Na+/H+ antiport. Half-maximal stimulation of H+ efflux occurred at approximately 10(-9) M, which is close to the dissociation constant of the cardiac angiotensin AT1 receptor. Stimulation via this receptor was confirmed with the nonpeptide AT1 receptor blocker, GR-117289. Angiotensin II had less pronounced effects on HCO3(-)-dependent pHi recovery after acid loading with no effect on pHi recovery after intracellular alkalosis. During reperfusion, angiotensin II significantly increased H+ extrusion but impaired contractile recovery. The results support the hypothesis that angiotensin II facilitates H+ extrusion in the heart. This may help maintain physiological homeostasis, but the hypothesized obligated Na+ influx could exacerbate cellular dysfunction during reperfusion.

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.

Ischemic preconditioning and intracellular pH: a 31P NMR study in the isolated rat heart

1997 ◽  
Vol 272 (1) ◽  
pp. H544-H552 ◽  
Author(s):  
A. C. Cave ◽  
P. B. Garlick
Keyword(s):  
Intracellular Ph ◽  
Recovery Of Function ◽  
Isolated Rat Heart ◽  
Rate Pressure Product ◽  
Intracellular Acidosis ◽  
Nmr Study ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Ischemic Period ◽  
Ethanesulfonic Acid

The aim of these studies was to investigate whether manipulation of intracellular pH affects preconditioning in isolated buffer-perfused rat hearts. Control and preconditioned [PC; 3 min of ischemia (I) + 3 min of reperfusion (R) + 5 min of I + 5 min of R or 4 x (5 min of I + 5 min of R)] hearts were subjected to two different protocols expected to alter intracellular pH during the sustained ischemic insult: 1) increased extracellular buffering capacity with the addition of 25 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) to the buffer to alleviate acidosis and 2) increased preischemic glycogen content to exacerbate acidosis. All hearts were subjected to 40 min of I + 40 min of R. 31P nuclear magnetic resonance was used to measure ATP, phosphocreatine, Pi, and intracellular pH. Despite a significantly better recovery of function in all PC groups, there were no significant differences in intracellular pH (rate-pressure product = 60 +/- 5, 66 +/- 10, 42 +/- 5, and 57 +/- 8% of baseline in PC, 4 x 5 PC, PC + HEPES, and PC fasted hearts, respectively, compared with 36 +/- 9, 17 +/- 7, and 20 +/- 10% of baseline in control, control + HEPES, and control fasted hearts, respectively; pH at end ischemia: control, 6.31 +/- 0.02; PC, 6.35 +/- 0.03; 4 x 5 PC, 6.35 +/- 0.04; control + HEPES, 6.40 +/- 0.10; PC + HEPES, 6.56 +/- 0.07: control fasted, 6.46 +/- 0.03; PC fasted, 6.43 +/- 0.01). No significant differences were observed among groups in ATP, phosphocreatine, or Pi on reperfusion. Thus the mechanism of preconditioning in glucose-perfused hearts does not depend on an alleviation of intracellular acidosis during the sustained ischemic period. Furthermore, under the conditions of this study, intracellular pH during ischemia did not predict functional recovery on reperfusion.

Effects of angiotensin II and vasopressin on intracellular pH of glomerular mesangial cells

1988 ◽  
Vol 254 (6) ◽  
pp. F787-F794 ◽  
Author(s):  
M. B. Ganz ◽  
G. Boyarsky ◽  
W. F. Boron ◽  
R. B. Sterzel
Keyword(s):  
Angiotensin Ii ◽  
Intracellular Ph ◽  
Mesangial Cells ◽  
Ang Ii ◽  
Glomerular Mesangial Cells ◽  
Initial Value ◽  
Ph Change ◽  
Acid Load ◽  
Ethanesulfonic Acid ◽  
Acid Extrusion

We investigated changes in intracellular pH (pHi) of cultured rat glomerular mesangial cells (MCs) exposed to angiotensin II (ANG II) and arginine vasopressin (AVP). pHi of quiescent MCs, passage 2–5, and grown on glass cover slips, was assessed by spectrofluorometry using the pH-sensitive dye, 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF). The steady-state pHi of MCs in a pH 7.4, HCO3-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered solution was 7.10 +/- 0.02 (n = 68) and in a pH 7.4, HCO3-containing solution, was 7.23 +/- 0.03 (n = 47) (P less than 0.01). The pHi recovery following an NH+4-induced acid load was inhibited by removal of Na+ from the bath or by addition of the amiloride analogue, ethyl isopropyl amiloride (EIPA). These effects were observed in MCs bathed in HEPES- or in HCO3-buffered solutions, consistent with the action of a Na+-H+ exchanger. When cells were bathed in HEPES, a 10-min exposure to ANG II or AVP (10(-10) to 10(-6) M) caused early and transient acidification of MCs (maximal pH change was -0.10), followed by gradual alkalinization (maximal pHi change +0.15 above the initial value). The increase of pHi was dependent on the presence of Na+ in the bath and was inhibited by EIPA. In the presence of HCO3, ANG II or AVP induced merely a small gradual acidification of MCs (pHi change -0.05). These findings demonstrate that MCs utilize a Na+-H+ exchanger for acid extrusion.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Intracellular pH regulation in isolated myocytes from adult rat heart in HCO-3-containing and HCO-3-free media

1993 ◽  
Vol 84 (2) ◽  
pp. 133-139 ◽  
Author(s):  
L. L. Ng ◽  
J. E. Davies ◽  
P. Quinn
Keyword(s):  
Intracellular Ph ◽  
Ventricular Myocytes ◽  
Ph Regulation ◽  
Specific Inhibitor ◽  
Buffering Capacity ◽  
Intracellular Acidosis ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Acid Load ◽  
Free Media

1. Using microfluorimetry, intracellular pH, buffering capacity and intracellular pH recovery from intracellular acidosis were determined in isolated adult rat ventricular myocytes, in buffers with and without HCO-3. 2. In nominally HCO-3-free media, the intracellular pH was higher than in HCO-3-containing media. Buffering capacity at resting intracellular pH and at a pH of about 6.3 was also lower in HCO-3-free media. 3. In HCO-3-free media, recovery from an acid load after an NH4C1 prepulse was almost completely inhibited by the Na+/H+ antiport activity specific inhibitor ethylisopropyl amiloride. However, in the presence of HCO-3, H+ efflux rate was enhanced, and ethylisopropyl amiloride led to only partial inhibition of H+ efflux. Complete inhibition was achieved only with further addition of the anion-transport inhibitor 4,4′-di-isothiocyanatostilbene-2,2′-disulphonate. 4. Thus, in adult rat ventricular myocytes, recovery from intracellular acidosis in the absence of HCO-3 was almost wholly due to Na+/H+ antiport activity. In the more physiological situation with HCO-3 present, a third of the recovery from an intracellular acid load was attributed to an additional external Na+-dependent di-isothiocyanatostilbene-disulphonate-sensitive H+ efflux.

Effect of ursodeoxycholic acid on intracellular pH regulation in isolated rat bile duct epithelial cells

1993 ◽  
Vol 265 (4) ◽  
pp. G783-G791 ◽  
Author(s):  
D. Alvaro ◽  
A. Mennone ◽  
J. L. Boyer
Keyword(s):  
Bile Duct ◽  
Ursodeoxycholic Acid ◽  
Cholic Acid ◽  
Intracellular Ph ◽  
Ph Regulation ◽  
Weak Acid ◽  
Normal Rat ◽  
Acid Load ◽  
Ethanesulfonic Acid ◽  
Isolated Rat

To determine if ursodeoxycholic acid (UDCA) induces a HCO3(-)-rich hypercholeresis by stimulating HCO3- secretion from bile duct epithelial (BDE) cells, we studied the effect of UDCA, sodium tauroursodeoxycholate (TUDCA), and cholic acid on intracellular pH (pHi) regulation and HCO3- excretion in BDE cells isolated from normal rat liver. Exposure of BDE cells to UDCA (0.5-1.5 mM) produced a dose-dependent initial acidification [from -0.05 to -0.16 pH units (pHu)], which was lower in Krebs-Ringer bicarbonate than in N-2-hydroxyethylpiperazine-N'-2- ethanesulfonic acid (HEPES), because of the higher cell-buffering power in the presence of HCO3-. In contrast, TUDCA (1 mM) had no effect on pHi in either media. BDE acidification induced by UDCA (1.5 mM) in KRB was not inhibited by Cl- depletion excluding activation of Cl(-)-HCO3- exchange. Most BDE cells spontaneously recovered their basal pHi during the UDCA infusion (0.5-1 mM) by a secondary activation of the Na(+)-H+ exchanger (amiloride inhibition of pHi recovery; n = 4), and pHi overshot basal levels by 0.1-0.2 pHu after UDCA withdrawal. The activity of Cl(-)-HCO3- exchange (Cl- removal/readmission maneuver) as well as the activities of Na(+)-H+ exchange and Na(+)-HCO3- symport (NH4Cl acid load in HEPES and KRB, respectively) were unaffected by UDCA (0.5 mM) compared with controls. Cholic acid (1.5 mM), which does not produce a hypercholeresis, also acidified BDE cells in KRB media. These studies indicate that UDCA does not stimulate HCO3- excretion from isolated rat BDE cells but modifies pHi in BDE cells as a weak acid.

Intersubject differences in the effect of acidosis on phosphocreatine recovery kinetics in muscle after exercise are due to differences in proton efflux rates

2007 ◽  
Vol 293 (1) ◽  
pp. C228-C237 ◽  
Author(s):  
Nicole M. A. van den Broek ◽  
Henk M. M. L. De Feyter ◽  
Larry de Graaf ◽  
Klaas Nicolay ◽  
Jeanine J. Prompers
Keyword(s):  
Ph Dependence ◽  
Resonance Spectroscopy ◽  
Muscle Exercise ◽  
Intracellular Acidosis ◽  
Proton Efflux ◽  
Efflux Rate ◽  
Cytosolic Ph ◽  
Efflux Rate Constant ◽  
And Control ◽  
Kinetics Of

31P magnetic resonance spectroscopy provides the possibility of obtaining bioenergetic data during skeletal muscle exercise and recovery. The time constant of phosphocreatine (PCr) recovery (τPCr) has been used as a measure of mitochondrial function. However, cytosolic pH has a strong influence on the kinetics of PCr recovery, and it has been suggested that τPCr should be normalized for end-exercise pH. A general correction can only be applied if there are no intersubject differences in the pH dependence of τPCr. We investigated the pH dependence of τPCr on a subject-by-subject basis. Furthermore, we determined the kinetics of proton efflux at the start of recovery. Intracellular acidosis slowed PCr recovery, and the pH dependence of τPCr differed among subjects, ranging from −33.0 to −75.3 s/pH unit. The slope of the relation between τPCr and end-exercise pH was positively correlated with both the proton efflux rate and the apparent proton efflux rate constant, indicating that subjects with a smaller pH dependence of τPCr have a higher proton efflux rate. Our study implies that simply correcting τPCr for end-exercise pH is not adequate, in particular when comparing patients and control subjects, because certain disorders are characterized by altered proton efflux from muscle fibers.

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