Figure 4.

CLSM images of [Ca²⁺]_i oscillations in a spontaneously contracting area of cardiomyocytes isolated from a stage-2 EB. (A) Control conditions. A [Ca²⁺]_i wave spread with a velocity of ≈400 μm⋅sec⁻¹ from the initiation site (cell 1) to the termination site (cell 4). The tracings of [Ca²⁺]_i changes in different cells (cell 1–4) demonstrate the synchronization of the [Ca²⁺]_i signal, indicating electrical coupling between adjacent cells. (B) [Ca²⁺]_i oscillations recorded in the same area of cardiomyocytes after superfusion with high K⁺. The images were recorded after decline toward resting [Ca²⁺]_i of the initial transient [Ca²⁺]_i rise after switching to high K⁺. The initial [Ca²⁺]_i increase was caused by the activation of VDCC. Note that, under high K⁺ [Ca²⁺]_i, oscillations in cells 1–4 are desynchronized and differ in amplitude and frequency.