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

2007 ◽  
Vol 130 (2) ◽  
pp. 133-144 ◽  
Author(s):  
Philipp Sasse ◽  
Jianbao Zhang ◽  
Lars Cleemann ◽  
Martin Morad ◽  
Juergen Hescheler ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Action Potentials ◽  
Embryonic Heart ◽  
Heart Cells ◽  
Periodic Oscillations ◽  
Mechanical Signals ◽  
Embryonic Cardiomyocytes

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.

Insulin-specific receptor-mediated slowing of beat rate in embryonic heart cells

1984 ◽  
Vol 246 (3) ◽  
pp. C347-C350 ◽  
Author(s):  
R. L. DeHaan ◽  
G. Goodrum ◽  
E. Strumlauf ◽  
L. J. Elsas
Keyword(s):  
Heart Rate ◽  
Action Potential Duration ◽  
Action Potentials ◽  
Embryonic Heart ◽  
Maximal Response ◽  
Heart Cells ◽  
Specific Receptor ◽  
High Affinity ◽  
Beat Rate ◽  
Pace Maker

Spheroidal aggregates of embryonic heart cells showed their spontaneous beat rate when exposed to insulin. The concentration that produced a half-maximal response (1.7 nM) corresponded to the dissociation constant of binding to a specific high-affinity insulin receptor. The pace-maker phase of action potentials recorded during insulin perfusion was preceded by a prolonged or flattened after hyperpolarization, and its slope was less steep than controls. The action potential duration was also prolonged. These results indicate that physiological concentrations of insulin can regulate the embryonic heart rate.

New Molecular Scaffolds for Fluorescent Voltage Indicators

2018 ◽  
Author(s):  
Steven Boggess ◽  
Shivaani Gandhi ◽  
Brian Siemons ◽  
Nathaniel Huebsch ◽  
Kevin Healy ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Action Potentials ◽  
Induced Pluripotent Stem Cell ◽  
Molecular Wire ◽  
Voltage Sensing ◽  
Design Synthesis ◽  
Cardiac Action ◽  
Action Potential Waveform ◽  
Induced Pluripotent ◽  
Voltage Sensing Domain

<div> <p>The ability to non-invasively monitor membrane potential dynamics in excitable cells like neurons and cardiomyocytes promises to revolutionize our understanding of the physiology and pathology of the brain and heart. Here, we report the design, synthesis, and application of a new class of fluorescent voltage indicator that makes use of a fluorene-based molecular wire as a voltage sensing domain to provide fast and sensitive measurements of membrane potential in both mammalian neurons and human-derived cardiomyocytes. We show that the best of the new probes, fluorene VoltageFluor 2 (fVF 2) readily reports on action potentials in mammalian neurons, detects perturbations to cardiac action potential waveform in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes, shows a substantial decrease in phototoxicity compared to existing molecular wire-based indicators, and can monitor cardiac action potentials for extended periods of time. Together, our results demonstrate the generalizability of a molecular wire approach to voltage sensing and highlights the utility of fVF 2 for interrogating membrane potential dynamics.</p> </div>

Membrane resistance increases when automaticity develops in explanted rat heart cells

1990 ◽  
Vol 258 (1) ◽  
pp. H145-H152 ◽  
Author(s):  
O. F. Schanne ◽  
M. Lefloch ◽  
B. Fermini ◽  
E. Ruiz-Petrich
Keyword(s):  
Spontaneous Activity ◽  
Action Potentials ◽  
Ventricular Myocytes ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Heart Cells ◽  
Membrane Capacity ◽  
Rat Heart Cells ◽  
Specific Membrane

We compared the passive electrical properties of isolated ventricular myocytes (resting potential -65 mV, fast action potentials, and no spontaneous activity) with those of 2- to 7-day-old cultured ventricle cells from neonatal rats (resting potential -50 mV, slow action potentials, and presence of spontaneous activity). In myocytes the specific membrane capacity was 0.99 microF/cm2, and the specific membrane resistance increased from 2.46 k omega.cm2 at -65 mV to 7.30 k omega.cm2 at -30 mV. In clusters, the current-voltage relationships measured under current-clamp conditions showed anomalous rectification and the input resistance decreased from 1.05 to 0.48 M omega when external K+ concentration was increased from 6 to 100 mM. Using the model of a finite disk we determined the specific membrane resistance (12.9 k omega.cm2), the effective membrane capacity (17.8 microF/cm2), and the lumped resistivity of the disk interior (1,964 omega.cm). We conclude that 1) the voltage dependence of the specific membrane resistance cannot completely explain the membrane resistance increase that accompanies the appearance of spontaneous activity; 2) a decrease of the inwardly rectifying conductance (gk1) is mainly responsible for the increase in the specific membrane resistance and depolarization; and 3) approximately 41% of the inward-rectifying channels are electrically silent when spontaneous activity develops in explanted ventricle cells.

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