Journal of Biomedical Science

, Volume 9, Issue 3, pp 198–205 | Cite as

Intracellular pH regulatory mechanism in human atrial myocardium: Functional evidence for Na+/H+ exchanger and Na+/HCO 3 symporter

  • Shih-Hurng Loh
  • Wei-Hwa Chen
  • Cheng-Hsien Chiang
  • Chien-Sung Tsai
  • Guo-Chen Lee
  • Jong-Shiaw Jin
  • Tzu-Hurng Cheng
  • Jin-Jer Chen
Original Paper


Intracellular pH (pHi) exerts considerable influence on cardiac contractility and rhythm. Over the last few years, extensive progress has been made in understanding the system that controls pHi in animal cardiomyocytes. In addition to the housekeeping Na+-H+ exchanger (NHE), the Na+-HCO 3 symporter (NHS) has been demonstrated in animal cardiomyocytes as another and extruder. However, whether the NHE and NHS functions exist in human atrial cardiomyocytes remains unclear. We therefore investigated the mechanism of pHi recovery from intracellular acidosis (induced by NH4Cl prepulse) using intracellular 2′,7′-bis(2-carboxethyl)-5(6)-carboxyfluorescein fluorescence in human atrial myocardium. In HEPES (nominally HCO 3 -free) Tyrode solution, pHi recovery from induced intracellular acidosis could be blocked completely by 30 µM 3-methylsulfonyl-4-piperidinobenzoyl, guanidine hydrochloride (HOE 694), a specific NHE inhibitor, or by removing extracellular Na+. In 3% CO2-HCO 3 Tyrode solution, HOE 694 only slowed the pHi recovery, while addition of HOE 694 together with 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (an NHS inhibitor) or removal of extracellular Na+ inhibited the acid extrusion entirely. Therefore, in the present study, we provided evidence that two acid extruders involved in acid extrusion in human atrial myocytes, one which is HCO 3 independent and one which is HCO 3 dependent, are mostly likely NHE and NHS, respectively. When we checked the percentage of contribution of these two carriers to pHi recovery following induced acidosis, we found that the activity of NHE increased steeply in the acid direction, while that of NHS did not change. Our present data indicate for the first time that two acid extruders, NHE and NHS, exist functionally and pHi dependently in human atrial cardiomyocytes.

Key Words

Intracellular pH BCECF fluorescence Na+-H+ exchanger Na+-HCO3 symporter Acid extruder Human atrium 


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  1. 1.
    Allen DG, Orchard CH. Myocardial contractile function during ischemia and hypoxia. Circ Res 60:153–168;1987.Google Scholar
  2. 2.
    Aronson PS. Kinetic properties of the plasma membrane Na+/H+ exchanger. Annu Rev Physiol 47:545–560;1985.Google Scholar
  3. 3.
    Bond JM, Herman B, Lemasters JJ. Protection by acidotic pH against anoxia/reoxygenation injury to rat neonatal cardiac myocytes. Biochem Biophys Res Commum 179:798–803;1991.Google Scholar
  4. 4.
    Bountra C, Vaughan-Jones RD. Effect of intra-cellular and extracellular pH on contraction in isolated, mammalian cardiac muscle. J Physiol 418:163–187;1989.Google Scholar
  5. 5.
    Camilion de Hurtado MC, Alvarez BV, Perez NG, Cingolani HE. Role of an electrogenic Na+-HCO3 cotransport in determining myocardial pHi after an increase in heart rate. Circ Res 79:698–704;1996.Google Scholar
  6. 6.
    Carbone E, Testa PL, Wanke E. Intracellular pH and ionic channels in the Loligo vulgaris giant axon. Biophys J 35:393–413;1981.Google Scholar
  7. 7.
    Counillon L, Scholz W, Lang HJ, Pouyssegur J. Pharmacological characterization of stably transfected Na+/H+ antiporter isoforms using amiloride analogs and a new inhibitor exhibiting anti-ischemic properties. Mol Pharmacol 44:1041–1045;1993.Google Scholar
  8. 8.
    Dart C, Vaughan-Jones RD. Na+-HCO3 symport in the sheep cardiac Purkinje fiber. J Physiol 451:365–385;1992.Google Scholar
  9. 9.
    Deitmer JW, Ellis D. Interactions between the regulation of the intracellular pH and sodium activity of sheep cardiac Purkinje fibres. J Physiol 304:471–488;1980.Google Scholar
  10. 10.
    Fliegel L, Sardet C, Pouyssegur J, Barr A. Identification of the protein and cDNA of the cardiac Na+/H+ exchanger. FEBS Lett 279:25–29;1991.Google Scholar
  11. 11.
    Frelin C, Vigne P, Lazdunski M. The role of the Na+/H+ exchange system in cardiac cells in relation to the control of the internal Na+ concentration. A molecular basis for the antagonistic effect of ouabain and amiloride on the heart. J Biol Chem 259:8880–8885;1984.Google Scholar
  12. 12.
    Frelin C, Vigne P, Lazdunski M. The role of the Na+/H+ exchange system in the regulation of the internal pH in cultured cardiac cells. Eur J Biochem 149:1–4;1985.Google Scholar
  13. 13.
    Grace AA, Kirschenlohr HL, Metcalfe JC, Smith GA, Weissberg RL, Cragoe EJ, Vandenberg JI. Regulation of intracellular pH in the perfused heart by external HCO3 and Na+-H exchange. Am J Physiol 265:H289-H298;1993.Google Scholar
  14. 14.
    Grinstein S, Rotin D, Mason MJ. Na+/H+ exchange and growth factor-induced cytosolic pH changes. Role in cellular proliferation. Biochim Biophys Acta 988:73–97;1989.Google Scholar
  15. 15.
    Grinstein S, Woodside M, Sardet C, Pouyssegur J, Rotin D. Activation of the Na+/H+ antiporter during cell volume regulation. Evidence for a phosphorylation-independent mechanism. J Biol Chem 267:23823–23828;1992.Google Scholar
  16. 16.
    Kaila K, Vaughan-Jones RD. Influence of sodium-hydrogen exchange on intracellular pH, sodium and tension in sheep cardiac Purkinje fibres. J Physiol 390:93–118;1987.Google Scholar
  17. 17.
    Karmazyn M, Moffat M. Role of Na+/H+ exchange in cardiac physiology and pathophysiology: Mediation of myocardial reperfusion injury by the pH paradox. Cardiovasc Res 27:915–924;1993.Google Scholar
  18. 18.
    Klanke C, Su YR, Callen DF, Wang Z, Meneton P, Baird N, Kandasamy RA, Orlowski J, Otterud BE, Leppert M, Shull GE, Menon A. Molecular cloning and physical and genetic mapping of a novel human Na+/H+ exchanger (NHE5/SLC9A5) to chromosome 16q22.1. Genomics 25:615–622;1995.Google Scholar
  19. 19.
    Lagadic-Gossmann D, Buckler KJ, Vaughan-Jones RD. Role of bicarbonate in pH recovery from intracellular acidosis in the guinea-pig ventricular myocyte. J Physiol 458:361–384;1992.Google Scholar
  20. 20.
    Lazdunski M, Frelin C, Vigne P. The sodium/hydrogen exchange system in cardiac cells: Its biochemical and pharmacological properties and its role in regulating internal concentrations of sodium and internal pH. J Mol Cell Cardiol 17:1029–1042;1985.Google Scholar
  21. 21.
    Leem CH, Lagadic-Gossmann D, Vaughan-Jones RD. Characterization of intracellular pH regulation in the guinea-pig ventricular myocyte. J Physiol 517:159–180;1999.Google Scholar
  22. 22.
    Lin CI, Chiu TH, Chiang BN, Cheng KK. Electromechanical effects of caffeine in isolated human atrial fibres. Cardiovasc Res 19:727–733;1985.Google Scholar
  23. 23.
    Liu S, Piwnica-Worms D, Lieberman M. Intracellular pH regulation in cultured embryonic chick heart cells. Na+-dependent Cl/HCO3 exchange. J Gen Physiol 96:11247–1269;1990.Google Scholar
  24. 24.
    Loh SH, Sun B, Vaughan-Jones RD. Effect of Hoe 694, a novel Na+-H+ exchange inhibitor, on intracellular pH regulation in the guinea-pig ventricular myocyte. Br J Pharmacol 118:1905–1912;1996.Google Scholar
  25. 25.
    Meng HP, Maddaford TG, Pirece GN. Effect of amiloride and selected analogues on post-ischemic recovery of cardiac contractile function. Am J Physiol 264:H1831-H1835;1993.Google Scholar
  26. 26.
    Orchard CH, Cingolani HE. Acidosis and arrhythmias in cardiac muscle. Cardiovasc Res 28:1312–1319;1994.Google Scholar
  27. 27.
    Orchard CH, Kentish JC. Effect of changes of pH on the contractile function of cardiac muscle. Am J Physiol 258:C967-C981;1990.Google Scholar
  28. 28.
    Orlowski J, Kandasamy RA, Shull GE. Molecular cloning of putative members of the Na+/H+ exchanger gene family. J Biol Chem 267:9331–9339;1992.Google Scholar
  29. 29.
    Piwnica-Worms D, Jacob R, Horres CR, Lieberman M. Na+-H+ exchange in cultured chick heart cells. J Gen Physiol 85:43–64;1985.Google Scholar
  30. 30.
    Roos A, Boron WF. Intracellular pH. Physiol Rev 61:296–434;1981.Google Scholar
  31. 31.
    Scholz W, Albus U, Lang HJ, Martorana PA, Englert HC, Scholkens BA. Hoe 694, a new Na+/H+ exchanger inhibitor and its effects in cardiac ischaemia. Br J Pharmacol 109:562–568;1993.Google Scholar
  32. 32.
    Schomig A, Kurz T, Richard G, Schomig E. Neuronal sodium homeostasis and axoplasmic amine concentration determine calcium-independent noradrenaline release in normoxic and ischaemic rat heart. Circ Res 63:214–226;1988.Google Scholar
  33. 33.
    Tani M, Neely JR. Role of intracellular Na+ in Ca2+ overload and depressed recovery of ventricular function of reperfused ischemic rat hearts. Possible involvement of H+-Na+ and Na+-Ca2+ exchange. Circ Res 65:1045–1056;1989.Google Scholar
  34. 34.
    Trivedi B, Danforth WH. Effect of pH on the kinetics of frog muscle phosphofructokinase. J Biol Chem 241:4110–4112;1966.Google Scholar
  35. 35.
    Weissberg PL, Little PJ, Cragoe Jr EJ, Bobik A. The pH of spontaneously beating cultured rat heart cells is regulated by an ATP-calmodulin-dependent Na+/H+ antiport. Circ Res 64:676–685;1989.Google Scholar
  36. 36.
    Wu ML, Tsai KL, Wang SM, Wu JC, Wang BS, Lee YT. Mechanism of hydrogen peroxide and hydroxyl free radical induced intracellular acidification in cultured rat cardiac myoblasts. Circ Res 78:564–572;1996.Google Scholar

Copyright information

© National Science Council 2002

Authors and Affiliations

  • Shih-Hurng Loh
    • 5
  • Wei-Hwa Chen
    • 1
  • Cheng-Hsien Chiang
    • 5
  • Chien-Sung Tsai
    • 2
  • Guo-Chen Lee
    • 2
  • Jong-Shiaw Jin
    • 3
  • Tzu-Hurng Cheng
    • 4
  • Jin-Jer Chen
    • 4
  1. 1.Department of GynecologyNational Defense Medical CenterTaipeiTaiwan, ROC
  2. 2.Department of Cardiovascular SurgeryNational Defense Medical CenterTaipeiTaiwan, ROC
  3. 3.Department of PathologyNational Defense Medical CenterTaipeiTaiwan, ROC
  4. 4.Institute of Biomedical Sciences, Academia SinicaTaipeiTaiwan, ROC
  5. 5.Department of PharmacologyNational Defense Medical CenterTaipeiTaiwan (ROC)

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