Fig. 4.

Ca²⁺ signaling during excitation-contraction coupling in atrial myocytes.

(A) Confocal images of a ventricular and an atrial myocyte from the same cat heart stained with the membrane-bound fluorescent dye Di-8-ANEPPS. The regular structures spaced in a sarcomeric pattern in the ventricular cell represent t-tubules. In contrast, the atrial myocyte is devoid of any t-tubular staining. (B) Ca²⁺ transient recorded in the confocal linescan mode. The scanned line was positioned perpendicular to the longitudinal axis of the cell (c). Electrical stimulation of the cell during acquisition of the linescan image triggered a ‘U’-shaped Ca²⁺ transient (b), indicating that [Ca²⁺]_i increased first at the periphery of the cell (a) before propagating towards the center of the myocyte. Panel d shows local Ca²⁺ transients measured in the subsarcolemmal space (ss) and the center of the cell (ct).

The Figure is modified with permission from [72].