Reduced L-type calcium current in the embryonic chick heart with persistent truncus arteriosus

Area of Science:

• Cardiovascular Physiology
• Developmental Biology
• Congenital Heart Disease Research

Background:

• Persistent truncus arteriosus is a severe congenital heart defect where the embryonic heart fails septation, resulting in a common outflow tract.
• Embryonic chick hearts with this defect show enlarged ventricles, indicated by increased ventricular to whole embryo weight.

Purpose of the Study:

• To investigate calcium currents in an experimental model of persistent truncus arteriosus in embryonic chick hearts.
• To determine the characteristics of T-type (ICa.T) and L-type (ICa.L) calcium currents in affected ventricular myocytes.

Main Methods:

• Electrophysiological examination of calcium currents in ventricular myocytes from day 11 embryonic chick hearts.
• Quantification of L-type calcium channels using radioligand binding assays with 1,4-dihydropyridine antagonists and agonists.

Main Results:

• Both ICa.T and ICa.L currents were present in ventricular myocytes from control and persistent truncus arteriosus hearts.
• Hearts with persistent truncus arteriosus displayed a twofold reduction in peak ICa.L magnitude at +10 mV.
• No significant change in the number of L-type calcium channels was detected via receptor binding assays.

Conclusions:

• The reduction in ICa.L magnitude in persistent truncus arteriosus is not due to a decreased number of L-type calcium channels.
• An L-channel regulatory mechanism, independent of protein synthesis, is likely affected by this congenital heart defect.
• Observed changes in calcium currents may reflect adaptations to excessive hemodynamic burden, similar to adult heart responses.