Na+/H+ Exchange In Cardiac Cells: Implications For Electrical And Mechanical Events During Intracellular pH Changes

  • F. V. Bielen
  • S. Bosteels
  • F. Verdonck
Conference paper
Part of the NATO ASI Series book series (volume 29)

Abstract

Intracellular acidification induced by changing from Hepes to a CO2/HCO 3 buffer results in an increase in the intracellular Na+ activity (ai Na). The exchanger is nearly inactive at intracellular pH (pHi) of 7.2 − 7.0 and is strongly activated at pHi below 7.0. The rate of rise in ai Na in conditions of a blocked Na+/K+ pump increases by a factor of 3.8 ± 0.9 (n=6) when pHi drops from 7.2 ± 0.1 in Hepes to 6.8 ± 0.1 in 15% CO2. Acid-induced increase in ai Na and accelerated rate of rise of ai Na can be blocked by amiloride (2.10−3 M) or by decreasing pHO to 6.7. The rise in ai Na is associated with the generation of a Na+/K+ pump-dependent outward current. At low pHO the increase in outward current is much smaller which demonstrates the absence of secondary pump stimulation when Na+/H+ exchange is inhibited. The Na+/K+ pump dependent hyperpolarization modifies spontaneous activity. Recovery of contractile force in an acid-loaded cell is related to the gain in ai Na.

Keywords

Ischemia Boron Bicarbonate Hepes Cardiol 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Boron WF, De Weer P (1976) Intracellular pH transients in squid giant axons caused by CO2, NH3, and metabolic inhibitors. J Gen Physiol 67: 91–112PubMedCrossRefGoogle Scholar
  2. Deitmer JW, Ellis D (1980) Interactions between the regulation of the intracellular pH and sodium activity of sheep cardiac Purkinje fibres. J Physiol 304: 471–488PubMedGoogle Scholar
  3. Eisner DA, Lederer WJ, Vaughan-Jones RD (1984) The quantitative relationship between twitch tension and intracellular sodium activity in sheep cardiac Purkinje fibres. J Physiol 355: 251–266PubMedGoogle Scholar
  4. Ellis D, MacLeod KT (1985) Sodium-dependent control of intracellular pH in Purkinje fibres of sheep heart. J Physiol 359: 81–105PubMedGoogle Scholar
  5. Fabiato A, Fabiato F (1978) Effects of pH on the myofilaments and the sarcoplasmic reticulum of skinned cells from cardiac and skeletal muscles. J Physiol 276: 233–255PubMedGoogle Scholar
  6. Freiin C, Vigne P, Lazdunski M (1985) The role of the Na+/H+ exchange system in the regulation of the internal pH in cultured cardiac cells. Eur J Biochem 149: 1–4CrossRefGoogle Scholar
  7. Glitsch HG (1982) Electrogenic Na pumping in the heart. Ann Rev Physiol 44: 389–400CrossRefGoogle Scholar
  8. Kaila K, Vaughan-Jones RD (1987) Influence of sodium-hydrogen exchange on intracellular pH, sodium and tension in sheep cardiac Purkinje fibres. J Physiol 390: 93–118PubMedGoogle Scholar
  9. Mahnensmith RL, Aronson PS (1985) The plasma membrane sodium-hydrogen exchanger and its role in physiological and pathophysiological processes. Circ Res 57: 773–788 )Google Scholar
  10. Moody WJr (1984) Effects of intracellular H+ on the electrical properties of excitable cells. Ann Rev Neurosci 7: 257–278PubMedCrossRefGoogle Scholar
  11. Piwnica-Worms D, Jacob R, Horres CR, Lieberman M (1985) Na/H exchange in cultured chick heart cells. J Gen Physiol 85: 43–64PubMedCrossRefGoogle Scholar
  12. Piwnica-Worms D, Jacob R, Shigeto N, Horres CR, Lieberman M (1986) Na/H exchange in cultured chick heart cells:secondary stimulation of electrogenic transport during recovery from intracellular acidosis. J Mol Cell Cardiol 18: 1109–1116PubMedCrossRefGoogle Scholar
  13. Sheu S, Fozzard HA (1982) Transmembrane Na+ and Ca2+ electrochemical gradients in cardiac muscle and their relationship to force development. J Gen Physiol 80: 325–351PubMedCrossRefGoogle Scholar
  14. Sonn JK, Lee CO (1988) Na+-Ca2+ exchange in regulation of contractility in canine cardiac Purkinje fibers. Am J Physiol 255: C278–C290PubMedGoogle Scholar
  15. Verdonck F, Glitsch HG, Pusch H (1982) Importance of electrogenic sodium extrusion for suppression of spontaneous activity in rabbit Purkinje fibres. Arch int Physiol Biochim 90: 36–37Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • F. V. Bielen
    • 1
  • S. Bosteels
    • 1
  • F. Verdonck
    • 1
  1. 1.Campus KortrijkUniversity of LeuvenKortrijkBelgium

Personalised recommendations