Intracellular Ca2+ Oscillations, a Potential Pacemaking Mechanism in Early Embryonic Heart Cells

P Sasse, J Zhang, L Cleemann, M Morad… - The Journal of general …, 2007 - rupress.org
P Sasse, J Zhang, L Cleemann, M Morad, J Hescheler, BK Fleischmann
The Journal of general physiology, 2007rupress.org
Early (E9. 5–E11. 5) embryonic heart cells beat spontaneously, even though the adult
pacemaking mechanisms are not yet fully established. Here we show that in isolated murine
early embryonic cardiomyocytes periodic oscillations of cytosolic Ca2+ occur and that these
induce contractions. The Ca2+ oscillations originate from the sarcoplasmic reticulum and
are dependent on the IP3 and the ryanodine receptor. The Ca2+ oscillations activate the
Na+-Ca2+ exchanger, giving rise to subthreshold depolarizations of the membrane potential …
Early (E9.5–E11.5) embryonic heart cells beat spontaneously, even though the adult pacemaking mechanisms are not yet fully established. Here we show that in isolated murine early embryonic cardiomyocytes periodic oscillations of cytosolic Ca2+ occur and that these induce contractions. The Ca2+ oscillations originate from the sarcoplasmic reticulum and are dependent on the IP3 and the ryanodine receptor. The Ca2+ oscillations activate the Na+-Ca2+ exchanger, giving rise to subthreshold depolarizations of the membrane potential and/or action potentials. Although early embryonic heart cells are voltage-independent Ca2+ oscillators, the generation of action potentials provides synchronization of the electrical and mechanical signals. Thus, Ca2+ oscillations pace early embryonic heart cells and the ensuing activation of the Na+-Ca2+ exchanger evokes small membrane depolarizations or action potentials.
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