Figure 3.

Electrophysiological Characteristics of IRX4-2-MB-Purified Ventricular Cardiomyocytes

(A) Representative action potentials of IRX4-2-MB-positive and -negative cells (upper panel) and primarily isolated mouse fetal ventricular and atrial cardiomyocytes (lower panel).

(B) Half action potential duration (APD₅₀) of IRX4-2-MB-positive and -negative cells and mouse fetal ventricular and atrial cardiomyocytes.

(C) The percentages of the action potential types recorded from IRX4-2-MB-positive cells. A-like, atrial-like AP; V-like, ventricular-like AP.

Action potentials were measured from 50 cells in each group (A–C).

(D) Representative spontaneous calcium transients in IRX4-2-MB-positive cardiomyocytes (upper panel), mouse primary fetal ventricular cardiomyocytes (middle panel), and mouse primary fetal atrial cardiomyocytes (lower panel). In each panel, calcium transients were recorded in the upper section, where increasing calcium is indicated by the change in color from dark blue to light blue, and fluorescence intensity was normalized to the baseline measured at time 0 (F_o).

(E) The averages of the beating frequency (BPM) and calcium amplitude (F/F₀) of IRX4-2-MB-positive cells and mouse fetal ventricular and atrial cardiomyocytes.

Calcium transient experiments were performed on 15 cells in each group (D and E).