Junctional resistance and action potential delay between embryonic heart cell aggregates

Area of Science:

• Cardiovascular Science
• Cellular Electrophysiology
• Biophysics

Background:

• Embryonic chick ventricle cells form spheroidal aggregates.
• These aggregates exhibit spontaneous, synchronized beating when brought into contact.
• Understanding electrical interaction between cardiac cell aggregates is crucial for developmental biology and tissue engineering.

Purpose of the Study:

• To quantify the electrical interaction between contacting embryonic chick ventricle cell aggregates.
• To establish a relationship between action potential delay and interaggregate coupling resistance.
• To investigate the influence of aggregate size, contact area, and extracellular potassium on electrical coupling.

Main Methods:

• Spheroidal aggregates of embryonic chick ventricle cells were cultured and brought into contact.
• Action potentials were recorded using intracellular and extracellular electrodes.
• Interaggregate coupling resistance (Rc) was measured by injecting current pulses.
• Action potential delay (L) between synchronized aggregates was determined.

Main Results:

• A linear relationship was observed between action potential delay (L) and coupling resistance (Rc) after beat synchrony was achieved.
• The ratio L/Rc varied with extracellular potassium concentration ([Ko+]): 3.7 ms/MΩ at 4.8 mM [Ko+] and 10.1 ms/MΩ at 1.3 mM [Ko+].
• Aggregate size, contact area, and [Ko+] were identified as key variables influencing the time course of coupling.

Conclusions:

• Action potential delay between heart cell aggregates can be quantitatively related to interaggregate coupling resistance.
• This study provides a method to assess electrical coupling in cardiac cell aggregates.
• The findings contribute to understanding electrical communication in developing cardiac tissue.