Pflügers Archiv

, Volume 393, Issue 2, pp 171–178 | Cite as

Intracellular calcium and sodium activity in sheep heart Purkinje fibres

Effect of changes of external sodium and intracellular pH
  • Donald M. Bers
  • David Ellis
Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiology


Intracellular Ca, Na and H selective microelectrodes were used to study the effects of reduction of the extracellular Na concentration, [Na]0, on the free intracellular Ca concentration, [Ca] i , Na activity, (a Na i ), and intracellular pH (pH i ) in sheep heart Purkinje fibres.
  1. 1.

    Reduction of [Na]0 from 140 mM to 14 mM produced a decrease ofa Na i , and increase of free [Ca] i , and normally an increase of resting tension.

  2. 2.

    Inhibition of the Na−K pump by 10−5 M acetylstrophanthidin produced a slow rise of [Ca] i and resting tension.

  3. 3.

    The magnitude of the increase of free [Ca] i (and tension) produced by [Na]0 reduction was greatly enhanced when the Na−K pump is inhibited by either acetylstrophanthidin or K-free solutions.

  4. 4.

    We suggest that this enhanced rise of free [Ca] i in the presence of Na−K pump inhibition is due to Ca loading of intracellular Ca buffering systems during the pump inhibition.

  5. 5.

    Addition of NH4Cl produced a transient decrease of free [Ca] i that accompanied an alkaline change in pH i . Removal of NH4Cl (which produced a transient intracellular acidification) produced a transient increase of free [Ca] i .


We conclude that a close relationship exists between the control of free [Ca] i and pH i which may be due to competition at, or common use of, intracellular buffering systems.

Key words

Sodium Calcium pH Purkinje fibres Heart Cardiac glycoside 


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Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • Donald M. Bers
    • 1
  • David Ellis
    • 1
  1. 1.Department of PhysiologyEdinburgh University Medical SchoolEdinburghUK

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