Pflügers Archiv

, Volume 429, Issue 6, pp 797–804 | Cite as

Intracellular citrate induces regenerative calcium release from sarcoplasmic reticulum in guinea-pig atrial myocytes

  • G. Callewaert
  • K. R. Sipido
  • E. Carmeliet
  • L. Pott
  • P. Lipp
Original Article Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiology


Ca2+ release from the sarcoplasmic reticulum was studied in voltage-clamped guinea-pig atrial myocytes. Cells were dialysed with a pipette solution containing the Ca2+ indicator 1- [2-amino-5-(6-carboxyindol-2-yl) phenoxy]-2-(2′-amino-5′-methylphenoxy) ethane-N,N,N′,N′-tetraacetic acid](Indo-1, 100 μM) and as main anion either chloride or the low-affinity Ca2+ buffer citrate. Intracellular Ca2+ transients (Cai transients) were elicited by depolarizations from a holding potential of −50 mV. In chloride-dialysed cells, Cai transients showed a bell-shaped dependence on the amplitude of the depolarizing pulse. In citratedialysed cells, membrane depolarizations were associated with a small rise in [Ca2+]i. These small changes in [Ca2+]i were either followed by a large Cai. transient or failed to induce large changes in [Ca2+]i. The peak amplitude of the large Cai transient did not vary with the amplitude of the depolarizing pulse. These results demonstrate that in the presence of intracellular chloride, Ca2+ release in atrial cells is a graded process triggered by Ca2+ influx. Using citrate as the main intracellular anoin, Ca2+ release triggered by Ca2+ entry was no longer graded but occurred in a regenerative manner. The results are discussed in terms of two models in which citrate, affects the spatial distribution of [Ca2+]i or the loading state of the sarcoplasmic reticulum.

Key words

Ca2+ release Sarcoplasmic reticulum Atrial myocyte Heart Citrate 


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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • G. Callewaert
    • 1
  • K. R. Sipido
    • 1
  • E. Carmeliet
    • 1
  • L. Pott
    • 2
  • P. Lipp
    • 3
  1. 1.Laboratory of PhysiologyUniversity of LeuvenLeuvenBelgium
  2. 2.Institute of PhysiologyRuhr UniversityBochumGermany
  3. 3.Department of PhysiologyUniversity of BerneBerneSwitzerland

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