Postnatal development of atrial repolarization in the mouse

Area of Science:

• Cardiovascular Physiology
• Cardiac Electrophysiology
• Ion Channel Biology

Background:

• Cardiac action potential duration (APD) is critical for normal heart function.
• Voltage-dependent K(+) currents play a key role in cardiac repolarization.
• Understanding developmental changes in ion channels is essential for cardiac health.

Purpose of the Study:

• To investigate the postnatal development of action potential duration (APD) and K(+) currents in mouse atrial myocytes.
• To compare K(+) channel expression levels in neonatal versus adult mouse atrial tissues.
• To correlate changes in K(+) currents with developmental alterations in APD.

Main Methods:

• Isolation of atrial myocytes from mice at postnatal days 1, 7, 20, and adulthood.
• Electrophysiological recordings to measure APD and various K(+) currents (I(Kur), I(K1), I(to), I(ss)).
• RNase protection assay and Western blot analysis to quantify K(+) channel expression.

Main Results:

• Significant upregulation of K(+) currents during postnatal development led to a marked shortening of APD.
• Ultrarapid delayed rectifier current (I(Kur)) emerged in adult atria; other currents like I(K1) and I(to) developed earlier.
• K(+) channel isoform expression levels increased postnatally, correlating with observed current density changes.

Conclusions:

• Each K(+) current exhibits a unique developmental trajectory in the mouse atrium.
• Developmental regulatory factors significantly influence K(+) channel function in cardiac repolarization.
• The mouse atrium serves as a valuable model for studying K(+) channel regulation mechanisms.