Key Points
- This research aims to explore how Na+/Ca2+ exchange contributes to cell contraction in neonatal versus adult rabbit cardiac myocytes.
- Measured Na+/Ca2+ exchange current and cell contraction amplitude in isolated neonatal and adult rabbit ventricular myocytes.
- Investigated the dependence of Na+/Ca2+ exchange on Ca2+ concentration, Na+ concentration, and membrane potential.
- Analyzed effects of 5 mM Ni2+ and nifedipine on contraction amplitudes.
- In neonatal myocytes, maximal contraction occurred at positive membrane potentials, while adult myocytes peaked at 0 mV and decreased thereafter.
- Inhibition of voltage-gated Ca2+ currents did not significantly impact contraction in neonatal cells but nearly abolished contraction in adult myocytes.
- Ca2+ influx via Na+/Ca2+ exchange significantly contributes to contraction in neonatal cells during depolarization.
Structured PICO
PPopulationSingle neonatal and adult rabbit ventricular myocytes
IInterventionDepolarization and pharmacological blockade (5 mM Ni2+ or nifedipine)
OOutcomeNa+/Ca2+ exchange current (INa/Ca) and cell contraction amplitudesurrogate
In neonatal rabbit cardiac myocytes, Ca2+ influx via reverse Na+/Ca2+ exchange, rather than voltage-gated Ca2+ channels, plays a major role in regulating cell contraction.