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Updated: Aug 20, 2026
Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
Published on: July 3, 2013
Calcium transients in infant human atrial myocytes
Mary B Wagner1, Yanggan Wang, Rajiv Kumar
1The Todd Franklin Cardiac Research Laboratory, The Sibley Children's Heart Center, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA.
Insights
Infant atrial cells show slower repolarization and lower calcium currents than adults. This delayed repolarization enhances the intracellular calcium transient, potentially compensating for reduced calcium availability in infant heart cells.
Area of Science:
- Cardiology
- Cell Physiology
- Developmental Biology
Background:
- Infant human atrial cells exhibit distinct electrophysiological properties compared to adult cells.
- Lower basal L-type calcium currents are observed in infant atrial myocytes.
Purpose of the Study:
- To investigate the hypothesis that slower early repolarization in infant atrial cells enhances the intracellular calcium transient.
- To understand the functional implications of electrophysiological differences in infant versus adult atrial cells.
Main Methods:
- Enzymatic dissociation of atrial myocytes from infant human atrial appendages.
- Measurement of intracellular calcium transients using fluorescence microscopy.
- Application of square wave and action potential waveforms at physiologic temperature.
Main Results:
- Shorter test pulse durations resulted in significantly smaller calcium transients in infant cells.
- Infant cells exhibited a decreased calcium transient when exposed to adult action potential waveforms compared to infant waveforms.
- Delayed early repolarization in infant cells was shown to alter the calcium transient.
Conclusions:
- The delayed early repolarization in infant atrial cells plays a crucial role in modulating the calcium transient.
- This alteration in calcium transient may serve as a compensatory mechanism for lower basal calcium currents in infant cells.
- Modulating the early repolarization phase of the action potential is significant for excitation-contraction coupling in the infant heart.
Abstract:
Isolated infant human atrial cells have a slower early repolarization than adult human atrial cells. In addition, from room temperature voltage-clamp studies, infant cells have lower basal L-type calcium currents than adult cells. We hypothesized that the slower repolarization increases the calcium transient of infant human atrial cells. Atrial myocytes were enzymatically dissociated from biopsies of human right atrial appendages of infant (3-8 mo) patients who were undergoing open-heart surgery. Intracellular calcium transients were measured with fluorescence microscopy with application of either square waves or action potential waveforms at physiologic temperature. After repetitive application (1 Hz) of 100-ms duration conditioning depolarizations to 10 mV (from -80 mV), a test pulse of varying duration (DeltaT; 2-100 ms) produced smaller transients (expressed as percentage of the last conditioning pulse) at shorter durations (33 +/- 7% for DeltaT = 2 ms, 80 +/- 4% for DeltaT = 25 ms). With repetitive application of either adult or infant prerecorded action potentials to infant cells, the cells had a decreased calcium transient with the adult action potential (F/F(0) 2.2 +/- 0.4 for infant action potential versus 1.6 +/- 0.2 for adult action potential; n = 7; p < 0.05). The delayed early repolarization of infant cells alters the Ca(2+) transient, which may compensate for the lower availability of basal calcium current in infant cells. The steep relationship that we have demonstrated between test-pulse duration and the calcium transient suggests that modulation of the early repolarization phase of the action potential may be of great significance in modulating excitation-contraction coupling.
