Developmental changes in calcium currents of rabbit ventricular cells.

Area of Science:

• Cardiovascular Physiology
• Cellular Electrophysiology
• Developmental Biology

Background:

• L-type Ca2+ current (ICa) is crucial for cardiac excitation-contraction coupling.
• Understanding developmental changes in cardiac ion channels is vital for pediatric cardiology.

Purpose of the Study:

• To investigate the postnatal developmental changes in L-type Ca2+ current (ICa) density and kinetics in rabbit ventricular cells.
• To compare ICa characteristics between newborn (NB) and adult (AD) rabbit ventricular myocytes.

Main Methods:

• Utilized the whole-cell patch-clamp technique on enzymatically isolated adult and newborn rabbit ventricular cells.
• Recorded ICa using Cs(+)-rich pipettes and a Na(+)- and K(+)-free bath solution at 36°C.
• Normalized ICa to cell capacitance to determine ICa density and analyzed current-voltage relationships and inactivation kinetics.

Main Results:

• Significantly higher ICa density was observed in adult ventricular cells compared to newborn cells across a range of membrane potentials (0 to +50 mV).
• Maximum ICa density was approximately 9.9 pA/pF in adult cells versus 5.6 pA/pF in newborn cells.
• Time to half inactivation (T 1/2) of ICa was slightly but significantly longer in newborn cells than in adult cells at potentials of 0 and +10 mV.

Conclusions:

• Postnatal development leads to a significant increase in L-type Ca2+ current density in rabbit ventricular myocytes.
• These developmental changes in ICa may contribute to altered cardiac contractility and electrophysiology in the transition from newborn to adult life.