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Intracellular calcium and sodium activity in sheep heart Purkinje fibres

Effect of changes of external sodium and intracellular pH

  • Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiology
  • Published:
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Abstract

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 iNa ), 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 iNa , 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.

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Author notes

  1. Donald M. Bers

    Present address: Department of Physiology, UCLA School of Medicine, A3-381 CHS, 90024, Los Angeles, CA, USA

Authors and Affiliations

  1. Department of Physiology, Edinburgh University Medical School, EH8 9AG, Edinburgh, UK

    Donald M. Bers & David Ellis

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  1. Donald M. Bers
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Bers, D.M., Ellis, D. Intracellular calcium and sodium activity in sheep heart Purkinje fibres. Pflugers Arch. 393, 171–178 (1982). https://doi.org/10.1007/BF00582941

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  • DOI: https://doi.org/10.1007/BF00582941

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